Method and apparatus for providing frequency band list in wireless communication system

ABSTRACT

A terminal for cell reselection in a wireless communication system includes: a transceiver; and at least one processor configured to select a Public Land Mobile Network (PLMN) in an idle mode or an inactive mode, receive, from a base station, a PLMN identity list including one or more pieces of PLMN identity information via a first type system information block, wherein each of the one or more pieces of PLMN identity information includes a PLMN identity for a corresponding PLMN, and the one or more pieces of PLMN identity information are listed in a first order for PLMN(s), receive, from the base station, a PLMN information list including one or more pieces of PLMN information via a third type system information block, wherein each of the one or more pieces of PLMN information includes a New Radio (NR) frequency band list for a corresponding PLMN in a same order as the first order for PLMN(s) in which the one or more pieces of PLMN identity information are listed in the PLMN identity list received via the first type system information block, determine whether at least one NR frequency for the selected PLMN is included in the NR frequency band list and whether the terminal supports to operate in E-UTRA-NR Dual Connectivity (EN-DC) by using the at least one NR frequency for the selected PLMN, when the at least one NR frequency for the selected PLMN is included in the NR frequency band list and the terminal supports to operate in the EN-DC by using the at least one NR frequency for the selected PLMN, transmit, to a upper layer, a upper layer indication, and when the at least one NR frequency for the selected PLMN is not included in the NR frequency band list or the terminal does not support to operate in the EN-DC by using the at least one NR frequency for the selected PLMN, transmit, to the upper layer, information indicating absence of the upper layer indication.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 U.S.C. § 119to Korean Patent Application No. 10-2020-0006774 filed on Jan. 17, 2020in the Korean Intellectual Property Office, the disclosure of which isincorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a method and apparatus for providing afrequency band list in a wireless communication system.

2. Description of Related Art

To meet the increase in demand with respect to wireless data trafficafter the commercialization of 4^(th) generation (4G) communicationsystems, considerable efforts have been made to develop pre-5^(th)generation (5G) communication systems or 5G communication systems. Thisis one reason why ‘5G communication systems’ or ‘pre-5G communicationsystems’ are called ‘beyond 4G network communication systems’ or ‘postLong-Term Evolution (LTE) systems.’ The 5G communication system definedin 3GPP is referred to as a new radio (NR) system. In order to achieve ahigh data rate, 5G communication systems are being developed to beimplemented in a super-high frequency band (millimeter wave (mmWave)),e.g., a band of 60 GHz. In order to reduce the path loss of radio wavesin such a super-high frequency band and to increase a transmissiondistance of radio waves in 5G communication systems, varioustechnologies are being studied, for example: beamforming, massivemultiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO),array antennas, analog beam-forming, and large-scale antennas, and havebeen applied to NR systems. In order to improve system networks for 5Gcommunication systems, various technologies have been developed, e.g.,evolved small cells, advanced small cells, cloud radio access networks(Cloud-RAN), ultra-dense networks, device-to-device communication (D2D),wireless backhaul, moving networks, cooperative communication,coordinated multi-points (CoMP), and interference cancellation. Also,for 5G communication systems, other technologies have been developed,e.g., hybrid frequency-shift keying (FSK) and quadrature amplitudemodulation (QAM) (FQAM) and sliding window superposition coding (SWSC),which are advanced coding modulation (ACM) schemes, and filter bankmulti carrier (FBMC), non-orthogonal multiple access (NOMA) and sparsecode multiple access (SCMA), which are advanced access schemes.

The Internet has evolved from a human-based connection network, wherehumans create and consume information, to the Internet of things (IoT),where distributed components, such as objects, exchange information witheach other to process the information. Internet of everything (IoE)technology is emerging, in which technology related to the IoT iscombined with, for example, technology for processing big data throughconnection with a cloud server. In order to implement the IoT, varioustechnological components are required, such as sensing technology,wired/wireless communication and network infrastructures, serviceinterface technology, security technology, etc. In recent years,technologies including a sensor network for connecting objects, machineto machine (M2M) communication, machine type communication (MTC), etc.have been studied. In the IoT environment, intelligent Internettechnology (IT) services may be provided to collect and analyze dataobtained from objects connected to each other to create new value inhuman life. As existing information technology (IT) techniques andvarious industries converge and combine with each other, the IoT may beapplied to various fields, such as smart homes, smart buildings, smartcities, smart cars or connected cars, smart grids, health care, smarthome appliances, high quality medical services, etc.

Various attempts are being made to apply 5G communication systems to theIoT network. For example, technologies related to sensor networks, M2Mcommunication, MTC, etc., are being implemented by using 5Gcommunication technology including beam-forming, MIMO, array antennas,etc. The application of cloud radio access network (RAN) as a big dataprocessing technology described above may be an example of convergenceof 5G communication technology and IoT technology.

SUMMARY

Provided are a method and apparatus for providing a frequency band listto a user equipment (UE) in a wireless communication system.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments of the disclosure.

According to an embodiment of the disclosure, a terminal for cellreselection in a wireless communication system includes: a transceiver;and at least one processor configured to select a Public Land MobileNetwork (PLMN) in an idle mode or an inactive mode, receive, from a basestation, a PLMN identity list including one or more pieces of PLMNidentity information via a first type system information block, whereineach of the one or more pieces of PLMN identity information includes aPLMN identity for a corresponding PLMN, and the one or more pieces ofPLMN identity information are listed in a first order for PLMN(s),receive, from the base station, a PLMN information list including one ormore pieces of PLMN information via a third type system informationblock, wherein each of the one or more pieces of PLMN informationincludes a New Radio (NR) frequency band list for a corresponding PLMNin a same order as the first order for PLMN(s) in which the one or morepieces of PLMN identity information are listed in the PLMN identity listreceived via the first type system information block, determine whetherat least one NR frequency for the selected PLMN is included in the NRfrequency band list and whether the terminal supports to operate inE-UTRA-NR Dual Connectivity (EN-DC) by using the at least one NRfrequency for the selected PLMN, when the at least one NR frequency forthe selected PLMN is included in the NR frequency band list and theterminal supports to operate in the EN-DC by using the at least one NRfrequency for the selected PLMN, transmit, to a upper layer, a upperlayer indication, and when the at least one NR frequency for theselected PLMN is not included in the NR frequency band list or theterminal does not support to operate in the EN-DC by using the at leastone NR frequency for the selected PLMN, transmit, to the upper layer,information indicating absence of the upper layer indication.

The at least one processor may be further configured to: receive, fromthe base station, the upper layer indication via a second type systeminformation block, and when the at least one NR frequency for theselected PLMN is included in the NR frequency band list and the terminalsupports to operate in the EN-DC by using the at least one NR frequencyfor the selected PLMN, transmit, to the upper layer, the upper layerindication regardless of the received the upper layer indication,wherein the upper layer indication may be an indication to the upperlayer that a cell for the selected PLMN offers NR capabilities.

The at least one processor may be further configured to: receive, fromthe base station, a Radio Resource Control (RRC) connectionreconfiguration message including information associated with NRconfiguration, determine whether the terminal is configured to operatein the EN-DC based on the received RRC connection reconfigurationmessage, transmit, to the upper layer, the upper layer indication whenthe terminal is configured to operate in the EN-DC, and transmit, to theupper layer, information indicating absence of the upper layer indicatorwhen the terminal is not configured to operate in the EN-DC.

The information associated with NR configuration may be transmitted tothe terminal in a connected mode within the RRC connectionreconfiguration message when at least one NR frequency band for theselected PLMN is supported.

The at least one processor may be further configured to transmit, to thebase station, capability information including at least one ofinformation indicating whether the terminal supports the EN-DC orinformation including NR bands supported by the terminal in the EN-DC.

According to an embodiment of the disclosure, a base station for cellreselection in a wireless communication system includes: a transceiver;and at least one processor configured to transmit, to a terminal, aPublic Land Mobile Network (PLMN) identity list including one or morepieces of PLMN identity information via a first type system informationblock, wherein each of the one or more pieces of PLMN identityinformation includes a PLMN identity for a corresponding PLMN, and theone or more pieces of PLMN identity information are listed in a firstorder for PLMN(s), and transmit, to the terminal, a PLMN informationlist including one or more pieces of PLMN information via a third typesystem information block, wherein each of the one or more pieces of PLMNinformation includes a New Radio (NR) frequency band list for acorresponding PLMN in a same order as the first order for PLMN(s) inwhich the one or more pieces of PLMN identity information are listed inthe PLMN identity list received via the first type system informationblock, wherein, when at least one NR frequency for a PLMN selected bythe terminal is included in the NR frequency band list and the terminalsupports to operate in E-UTRA-NR Dual Connectivity (EN-DC) by using theat least one NR frequency for the PLMN selected by the terminal, a upperlayer indication is transmitted to a upper layer of the terminal, andwherein, when the at least one NR frequency for the PLMN selected by theterminal is not included in the NR frequency band list or the terminaldoes not support to operate in the EN-DC by using the at least one NRfrequency for the PLMN selected by the terminal, information indicatingabsence of the upper layer indication is transmitted to the upper layerof the terminal.

The at least one processor may be further configured to transmit, to theterminal, the upper layer indication via a second type systeminformation block, and wherein, when the at least one NR frequency forthe PLMN selected by the terminal is included in the NR frequency bandlist and the terminal supports to operate in the EN-DC by using the atleast one NR frequency for the PLMN selected by the terminal, the upperlayer indication may be transmitted to the upper layer of the terminalregardless of the received the upper layer indication, and wherein theupper layer indication may be an indication to the upper layer that acell for the PLMN selected by the terminal offers NR capabilities.

The at least one processor may be further configured to transmit, to theterminal, a Radio Resource Control (RRC) connection reconfigurationmessage including information associated with NR configuration, wherein,when the terminal is configured to operate in the EN-DC based on theinformation associated with NR configuration, the upper layer indicationmay be transmitted to the upper layer of the terminal, and wherein, whenthe terminal is not configured to operate in the EN-DC based on theinformation associated with NR configuration, the information indicatingabsence of the upper layer indicator may be transmitted to the upperlayer of the terminal.

The information associated with NR configuration may be transmitted tothe terminal in a connected mode within the RRC connectionreconfiguration message when at least one NR frequency band for theselected PLMN is supported.

The at least one processor may be further configured to receive, fromthe terminal, capability information including at least one ofinformation indicating whether the terminal supports the EN-DC orinformation including NR bands supported by the terminal in the EN-DC.

According to an embodiment of the disclosure, a method, performed by aterminal, for cell reselection in a wireless communication systemincludes: selecting a Public Land Mobile Network (PLMN) in an idle modeor an inactive mode; receiving, from a base station, a PLMN identitylist including one or more pieces of PLMN identity information via afirst type system information block, wherein each of the one or morepieces of PLMN identity information includes a PLMN identity for acorresponding PLMN, and the one or more pieces of PLMN identityinformation are listed in a first order for PLMN(s); receiving, from thebase station, a PLMN information list including one or more pieces ofPLMN information via a third type system information block, wherein eachof the one or more pieces of PLMN information includes a New Radio (NR)frequency band list for a corresponding PLMN in a same order as thefirst order for PLMN(s) in which the one or more pieces of PLMN identityinformation are listed in the PLMN identity list received via the firsttype system information block; determining whether at least one NRfrequency for the selected PLMN is included in the NR frequency bandlist and whether the terminal supports to operate in E-UTRA-NR DualConnectivity (EN-DC) by using the at least one NR frequency for theselected PLMN; when the at least one NR frequency for the selected PLMNis included in the NR frequency band list and the terminal supports tooperate in the EN-DC by using the at least one NR frequency for theselected PLMN, transmitting, to a upper layer, a upper layer indication;and when the at least one NR frequency for the selected PLMN is notincluded in the NR frequency band list or the terminal does not supportto operate in the EN-DC by using the at least one NR frequency for theselected PLMN, transmitting, to the upper layer, information indicatingabsence of the upper layer indication.

The method may further include receiving, from the base station, theupper layer indication via a second type system information block,wherein the transmitting the upper layer indication may include, whenthe at least one NR frequency for the selected PLMN is included in theNR frequency band list and the terminal supports to operate in the EN-DCby using the at least one NR frequency for the selected PLMN,transmitting, to the upper layer, the upper layer indication regardlessof the received the upper layer indication, and wherein the upper layerindication may be an indication to the upper layer that a cell for theselected PLMN offers NR capabilities.

The method may further include: receiving, from the base station, aRadio Resource Control (RRC) connection reconfiguration messageincluding information associated with NR configuration; determiningwhether the terminal is configured to operate in the EN-DC based on thereceived RRC connection reconfiguration message; transmitting, to theupper layer, the upper layer indication when the terminal is configuredto operate in the EN-DC; and transmitting, to the upper layer,information indicating absence of the upper layer indicator when theterminal is not configured to operate in the EN-DC.

The information associated with NR configuration may be transmitted tothe terminal in a connected mode within the RRC connectionreconfiguration message when at least one NR frequency band for theselected PLMN is supported.

The method may further include transmitting, to the base station,capability information including at least one of information indicatingwhether the terminal supports the EN-DC or information including NRbands supported by the terminal in the EN-DC.

According to an embodiment of the disclosure, a method, performed by abase station, for cell reselection in a wireless communication systemincludes: transmitting, to a terminal, a Public Land Mobile Network(PLMN) identity list including one or more pieces of PLMN identityinformation via a first type system information block, wherein each ofthe one or more pieces of PLMN identity information includes a PLMNidentity for a corresponding PLMN, and the one or more pieces of PLMNidentity information are listed in a first order for PLMN(s); andtransmitting, to the terminal, a PLMN information list including one ormore pieces of PLMN information via a third type system informationblock, wherein each of the one or more pieces of PLMN informationincludes a New Radio (NR) frequency band list for a corresponding PLMNin a same order as the first order for PLMN(s) in which the one or morepieces of PLMN identity information are listed in the PLMN identity listreceived via the first type system information block, wherein, when atleast one NR frequency for a PLMN selected by the terminal is includedin the NR frequency band list and the terminal supports to operate inE-UTRA-NR Dual Connectivity (EN-DC) by using the at least one NRfrequency for the PLMN selected by the terminal, a upper layerindication is transmitted to a upper layer of the terminal, and wherein,when the at least one NR frequency for the PLMN selected by the terminalis not included in the NR frequency band list or the terminal does notsupport to operate in the EN-DC by using the at least one NR frequencyfor the PLMN selected by the terminal, information indicating absence ofthe upper layer indication is transmitted to the upper layer of theterminal.

The method may further include transmitting, to the terminal, the upperlayer indication via a second type system information block, wherein,when the at least one NR frequency for the PLMN selected by the terminalis included in the NR frequency band list and the terminal supports tooperate in the EN-DC by using the at least one NR frequency for the PLMNselected by the terminal, the upper layer indication is transmitted tothe upper layer of the terminal regardless of the received the upperlayer indication, and wherein the upper layer indication is anindication to the upper layer that a cell for the PLMN selected by theterminal offers NR capabilities.

The method may further include transmitting, to the terminal, a RadioResource Control (RRC) connection reconfiguration message includinginformation associated with NR configuration, wherein, when the terminalis configured to operate in the EN-DC based on the informationassociated with NR configuration, the upper layer indication may betransmitted to the upper layer of the terminal, and wherein, when theterminal is not configured to operate in the EN-DC based on theinformation associated with NR configuration, the information indicatingabsence of the upper layer indicator may be transmitted to the upperlayer of the terminal.

The information associated with NR configuration may be transmitted tothe terminal in a connected mode within the RRC connectionreconfiguration message when at least one NR frequency band for theselected PLMN is supported.

The method may further include receiving, from the terminal, capabilityinformation including at least one of information indicating whether theterminal supports the EN-DC or information including NR bands supportedby the terminal in the EN-DC.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1A is a diagram of a structure of a long-term evolution (LTE)system, according to an embodiment of the disclosure;

FIG. 1B is a diagram of a radio protocol architecture in an LTE system,according to an embodiment of the disclosure;

FIG. 1C is a diagram of a structure of a next-generation mobilecommunication system, according to an embodiment of the disclosure;

FIG. 1D is a diagram of a radio protocol architecture of anext-generation mobile communication system, according to an embodimentof the disclosure;

FIG. 1E is a diagram for describing a procedure of determining that auser equipment (UE) in a radio resource control (RRC) idle mode or RRCinactive mode is located in a certain coverage area, according to anembodiment of the disclosure;

FIG. 1F is a diagram for describing a procedure of determining whether aUE in an RRC idle mode or RRC inactive mode supports a certain frequencyband, according to an embodiment of the disclosure;

FIG. 1G is a diagram for describing a procedure of determining whether aUE in an RRC idle mode or RRC inactive mode supports a certain frequencyband, according to an embodiment of the disclosure;

FIG. 1H is a diagram for describing a procedure of determining whether aUE in an RRC idle mode or RRC inactive mode supports a certain frequencyband, according to an embodiment of the disclosure;

FIG. 1I is a diagram for describing a procedure of determining whether aUE in an RRC idle mode or RRC inactive mode supports a certain frequencyband, according to an embodiment of the disclosure;

FIG. 1J is a diagram for describing a procedure of determining whether acertain frequency band is supported, according to an embodiment of thedisclosure;

FIG. 1K is a diagram for describing a procedure of determining whether acertain frequency range is supported, according to an embodiment of thedisclosure;

FIG. 1L is a diagram for describing a procedure of determining whether acertain frequency band is supported, according to an embodiment of thedisclosure;

FIG. 1M is a diagram for describing a procedure of determining whether acertain frequency band or frequency range is supported, according to anembodiment of the disclosure;

FIG. 1N is a block diagram showing an internal structure of a UE,according to an embodiment of the disclosure; and

FIG. 1O is a block diagram of a configuration of a base station,according to an embodiment of the disclosure.

DETAILED DESCRIPTION

FIGS. 1A through 10, discussed below, and the various embodiments usedto describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

Hereinafter, operation principles of the disclosure will be describedwith reference to accompanying drawings. While describing thedisclosure, detailed description of related well-known functions orconfigurations may be omitted when it is deemed that they mayunnecessarily obscure the essence of the disclosure. Also, terms usedbelow are defined in consideration of functions in the disclosure, andmay have different meanings according to an intention of a user oroperator, customs, or the like. Thus, the terms should be defined basedon the description throughout the specification.

While describing the disclosure, detailed description of relatedwell-known functions or configurations may be omitted when it is deemedthat they may unnecessarily obscure the essence of the disclosure.Hereinafter, embodiments of the disclosure will be described withreference to accompanying drawings.

Throughout the disclosure, the expression “at least one of a, b or c”indicates only a, only b, only c, both a and b, both a and c, both b andc, all of a, b, and c, or variations thereof.

Examples of a terminal may include a user equipment (UE), a mobilestation (MS), a cellular phone, a smartphone, a computer, a multimediasystem capable of performing a communication function, or the like.

In the disclosure, a controller may also be referred to as a processor.

Throughout the specification, a layer (or a layer apparatus) may also bereferred to as an entity.

Also, terms for identifying access nodes, terms denoting networkentities, terms denoting messages, terms denoting interfaces betweennetwork entities, terms denoting various types of identificationinformation, etc. used herein are exemplified for convenience ofdescription. Thus, the terms used in the disclosure are not limited andother terms denoting targets having the same technical meanings may beused.

Hereinafter, for convenience of description, the disclosure uses termsand names defined by the 3rd generation partnership project long termevolution (3GPP LTE) standard. However, the disclosure is not limited bysuch terms and names, and may be equally applied to systems conformingto other standards. In the disclosure, an evolved node B (eNB) will beused interchangeably with a next generation node B (gNB) for convenienceof description. In other words, a base station described as an eNB mayalso indicate a gNB.

Referring to FIG. 1A, a radio access network (RAN) of an LTE system mayinclude evolved node Bs (eNBs) 1 a-05, 1 a-10, 1 a-15, and 1 a-20 (nodeBs (NBs) or base stations), a mobility management entity (MME) 1 a-25,and a serving-gateway (S-GW) 1 a-30. A UE 1 a-35 (or a terminal) mayaccess an external network via the eNB 1 a-05, 1 a-10, 1 a-15, or 1 a-20and the S-GW 1 a-30.

In FIG. 1A, the eNBs 1 a-05 through 1 a-20 may correspond to existingNBs of a universal mobile telecommunication system (UMTS). The eNB 1a-05, 1 a-10, 1 a-15, or 1 a-20 may be connected to the UE 1 a-35through a radio channel and may perform complex functions compared tothe existing NB. In the LTE system, all user traffic including areal-time service such as voice over internet protocol (VoIP) may beprovided via a shared channel. Accordingly, an entity that schedules theUEs 1 a-35 by gathering state information such as buffer states,available transmit power states, and channel states of the UEs 1 a-35 isrequired, and the eNB 1 a-05, 1 a-10, 1 a-15, or 1 a-20 may operate asthe entity.

A single eNB may generally control multiple cells. For example, the LTEsystem may use radio access technology such as orthogonal frequencydivision multiplexing (OFDM) at a bandwidth of 20 MHz to achieve a datarate of 100 Mbps. Also, an adaptive modulation and coding (AMC) schememay be used to determine a modulation scheme and a channel coding ratein accordance with the channel state of the UE 1 a-35. The S-GW 1 a-30is an entity for providing data bearers and may configure or release thedata bearers under the control of the MME 1 a-25. The MME 1 a-25 is anentity for performing a mobility management function and various controlfunctions for the UE 1 a-35 and may be connected to the eNBs 1 a-05, 1a-10, 1 a-15, and 1 a-20.

FIG. 1B is a diagram of a radio protocol architecture in an LTE system,according to an embodiment of the disclosure.

Referring to FIG. 1B, a radio protocol of the LTE system may includepacket data convergence protocol (PDCP) layers 1 b-05 and 1 b-40, radiolink control (RLC) layers 1 b-10 and 1 b-35, and media access control(MAC) layers 1 b-15 and 1 b-30 respectively for a UE and an eNB. ThePDCP layer 1 b-05 or 1 b-40 may perform operations such as internetprotocol (IP) header compression/restoration. Main functions of the PDCPlayer 1 b-05 or 1 b-40 may be summarized as below.

-   -   Header compression and decompression: Robust header compression        (ROHC) only    -   Transfer of user data    -   In-sequence delivery of upper layer packet data units (PDUs) at        PDCP re-establishment procedure for RLC acknowledged mode (AM)    -   For split bearers in dual connectivity (DC) (only support for        RLC AM): PDCP PDU routing for transmission and PDCP PDU        reordering for reception)    -   Duplicate detection of lower layer service data units (SDUs) at        PDCP re-establishment procedure for RLC AM    -   Retransmission of PDCP SDUs at handover and, for split bearers        in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM    -   Ciphering and deciphering    -   Timer-based SDU discard in uplink

The RLC layer 1 b-10 or 1 b-35 may perform, for example, an automaticrequest for repetition (ARQ) operation by reconfiguring PDCP PDUs toappropriate sizes. Main functions of the RLC layer 1 b-10 or 1 b-35 maybe summarized as below.

-   -   Transfer of upper layer PDUs    -   Error Correction through ARQ (only for AM data transfer)    -   Concatenation, segmentation, and reassembly of RLC SDUs (only        for unacknowledged mode (UM) and AM data transfer)    -   Re-segmentation of RLC data PDUs (only for AM data transfer)    -   Reordering of RLC data PDUs (only for UM and AM data transfer)    -   Duplicate detection (only for UM and AM data transfer)    -   Protocol error detection (only for AM data transfer)    -   RLC SDU discard (only for UM and AM data transfer)    -   RLC re-establishment

The MAC layer 1 b-15 or 1 b-30 is connected to multiple RLC layersconfigured for a single UE and may multiplex RLC PDUs into a MAC PDU anddemultiplex the RLC PDUs from the MAC PDU. Main functions of the MAClayer 1 b-15 or 1 b-30 may be summarized as below.

-   -   Mapping between logical channels and transport channels    -   Multiplexing/demultiplexing of MAC SDUs belonging to one or        different logical channels into/from transport blocks (TBs)        delivered to/from the physical layer on transport channels    -   Scheduling information reporting    -   Error correction through HARQ    -   Priority handling between logical channels of one UE    -   Priority handling between UEs by means of dynamic scheduling    -   Multimedia broadcast multicast service (MBMS) identification    -   Transport format selection    -   Padding

A physical layer 1 b-20 or 1 b-25 may channel-code and modulate upperlayer data into OFDM symbols and transmit the OFDM symbols through aradio channel, or demodulate OFDM symbols received through a radiochannel and channel-decode and deliver the OFDM symbols to an upperlayer.

FIG. 1C is a diagram of a structure of a next-generation mobilecommunication system, according to an embodiment of the disclosure.

Referring to FIG. 1C, a RAN of a next-generation mobile communicationsystem (hereinafter, NR or 5G) may include an NR gNB 1 c-10 (or NR basestation) and an NR core network (CN) 1 c-05. An NR UE 1 c-15 (or aterminal) may access an external network via the NR gNB 1 c-10 and theNR CN 1 c-05.

In FIG. 1C, the NR gNB 1 c-10 may correspond to an eNB of an existingLTE system. The NR gNB 1 c-10 is connected to the NR UE 1 c-15 throughradio channels and may provide superior services compared to an existingNB. In the next-generation mobile communication system, all user trafficmay be provided via a shared channel. Accordingly, an entity thatschedules NR UEs 1 c-15 by gathering state information such as bufferstates, available transmit power states, and channel states of the NRUEs 1 c-15 is required, and the NR gNB 1 c-10 may operate as the entity.A single NR gNB 1 c-10 may control a plurality of cells. In thenext-generation mobile communication system, a bandwidth equal to orgreater than a current maximum bandwidth may be applied to implement anultra-high data rate compared to a current LTE system. Also, abeamforming technique may be grafted by using OFDM as a radio accesstechnique. Also, an AMC scheme may be used to determine a modulationscheme and a channel coding rate in accordance with a channel state ofthe NR UE 1 c-15. The NR CN 1 c-05 may perform functions such asmobility support, bearer setup, and quality of service (QoS) setup. TheNR CN 1 c-05 is an entity for performing a mobility management functionand various control functions for the NR UE 1 c-15 and may be connectedto a plurality of the NR gNBs 1 c-10. The next-generation mobilecommunication system may cooperate with the existing LTE system, and theNR CN 1 c-05 may be connected to an MME 1 c-25 through a networkinterface. The MME 1 c-25 may be connected to an eNB 1 c-30 that is anexisting base station.

FIG. 1D is a diagram of a radio protocol architecture of anext-generation mobile communication system, according to an embodimentof the disclosure.

Referring to FIG. 1D, a radio protocol of the next-generation mobilecommunication system may include NR service data adaptation protocol(SDAP) layers 1 d-01 and 1 d-45, NR PDCP layers 1 d-05 and 1 d-40, NRRLC layers 1 d-10 and 1 d-35, NR MAC layers 1 d-15 and 1 d-30, and NRphysical (PHY) layers 1 d-20 and 1 d-25 respectively for a UE and an NRgNB.

Main functions of the NR SDAP layers 1 d-01 and 1 d-45 may include someof the following functions.

-   -   Transfer of user plane data    -   Mapping between QoS flow and a data radio bearer (DRB) for both        downlink (DL) and uplink (UL)    -   Marking QoS flow ID in both DL and UL packets    -   Reflective QoS flow to DRB mapping for the UL SDAP PDUs

For the NR SDAP layer 1 d-01 or 1 d-45, the UE may be configured withwhether to use a header of the NR SDAP layer 1 d-01 or 1 d-45 for eachNR PDCP layer 1 d-05 or 1 d-40, bearer, or logical channel or whether touse a function of the NR SDAP layer 1 d-01 or 1 d-45 via an RRC message.When a SDAP header is configured, a 1-bit non-access stratum (NAS)reflective QoS configuration indicator and a 1-bit access stratum (AS)reflective QoS configuration indicator of the SDAP header may indicatethe UE to update or reconfigure mapping information between a QoS flowand a data bearer for both UL and DL. The SDAP header may include QoSflow ID indicating QoS. QoS information may be used as data processingpriority information, scheduling information, etc. for supporting asmooth service.

Main functions of the NR PDCP layer 1 d-05 or 1 d-40 may include some ofthe following functions.

-   -   Header compression and decompression: ROHC only    -   Transfer of user data    -   In-sequence delivery of upper layer PDUs    -   Out-of-sequence delivery of upper layer PDUs    -   PDCP PDU reordering for reception    -   Duplicate detection of lower layer SDUs    -   Retransmission of PDCP SDUs    -   Ciphering and deciphering    -   Timer-based SDU discard in uplink

A reordering function of the NR PDCP layer 1 d-05 or 1 d-40 may includedenote a function of reordering PDCP PDUs received from a lower layer,based on a PDCP sequence number (SN). The reordering function of the NRPDCP layer 1 d-05 or 1 d-40 may include a function of delivering thereordered data to an upper layer in order or a function of immediatelydelivering the reordered data without considering an order, may includea function of recording missing PDCP PDUs by reordering the PDCP PDUs,may include a function of reporting state information of the missingPDCP PDUs to a transmitter, and may include a function of requesting toretransmit the missing PDCP PDUs.

The main functions of the NR RLC layer 1 d-10 or 1 d-35 may include atleast some of the following functions.

-   -   Transfer of upper layer PDUs    -   In-sequence delivery of upper layer PDUs    -   Out-of-sequence delivery of upper layer PDUs    -   Error correction through ARQ    -   Concatenation, segmentation and reassembly of RLC SDUs    -   Re-segmentation of RLC data PDUs    -   Reordering of RLC data PDUs    -   Duplicate detection    -   Protocol error detection    -   RLC SDU discard    -   RLC re-establishment

The in-sequence delivery function of the NR RLC layer 1 d-10 or 1 d-35may denote a function of delivering RLC SDUs received from a lowerlayer, to an upper layer in order. When one RLC SDU is segmented into aplurality of RLC SDUs and received, the in-sequence delivery of the NRRLC layer 1 d-10 or 1 d-35 may include reassembly and deliveryfunctions.

The in-sequence delivery of the NR RLC layer 1 d-10 or 1 d-35 mayinclude a function of reordering received RLC PDUs on an RLC SN or PDCPSN basis, a function of recording missing RLC PDUs by reordering the RLCPDUs, a function of reporting state information of the missing RLC PDUsto a transmitter, and a function of requesting to retransmit the missingRLC PDUs. The in-sequence delivery of the NR RLC layer 1 d-10 or 1 d-35may include a function of delivering only RLC SDUs previous to a missingRLC SDU, to the upper entity in order, when the missing RLC SDU exists.The in-sequence delivery of the NR RLC layer 1 d-10 or 1 d-35 mayinclude a function of delivering all RLC SDUs received before a certaintimer started, to the upper entity in order, when the certain timerexpired despite of a missing RLS SDU. The in-sequence delivery of the NRRLC layer 1 d-10 or 1 d-35 may include a function of delivering all RLCSDUs currently received to the upper entity in order, when a certaintimer expired despite of a missing RLS SDU.

The NR RLC layer 1 d-10 or 1 d-35 may process the RLC PDUs in an orderof reception regardless of an order of sequence numbers (out-of-sequencedelivery) and deliver the same to the NR PDCP layer 1 d-05 or 1 d-40.

When the NR RLC layer 1 d-10 or 1 d-35 receives segments, the NR RLClayer 1 d-10 or 1 d-35 may reassemble the segments to be received lateror stored in a buffer, into a whole RLC PDU, process the hole RLC PDUand deliver the same to the NR PDCP layer 1 d-05 or 1 d-40.

The NR RLC layer 1 d-10 or 1 d-35 may not have a concatenation function,and the concatenation function may be performed by the NR MAC layer 1d-15 or 1 d-30 or be replaced with a multiplexing function of the NR MAClayer 1 d-15 or 1 d-30.

In the above description, out-of-sequence delivery of the NR RLC layer 1d-10 or 1 d-35 may denote a function of delivering RLC SDUs receivedfrom a lower layer, immediately to an upper layer out of an order. Theout-of-sequence delivery of the NR RLC layer 1 d-10 or 1 d-35 mayinclude a function of reassembling several RLC SDUs when originally oneRLC SDU is segmented and received in the several RLC SDUs. Theout-of-sequence delivery of the NR RLC layer 1 d-10 or 1 d-35 mayinclude a function of storing RLC SNs or PDCP SNs of received RLC PDUsand recording missing RLC PDUs by aligning the received RLC PDUs in anorder.

The NR MAC layer 1 d-15 or 1 d-30 may be connected to multiple NR RLClayers 1 d-10 or 1 d-35 configured for a single UE, and main functionsof the NR MAC layer 1 d-15 or 1 d-30 may include at least some of thefollowing functions.

-   -   Mapping between logical channels and transport channels    -   Multiplexing/demultiplexing of MAC SDUs    -   Scheduling information reporting    -   Error correction through HARQ    -   Priority handling between logical channels of one UE    -   Priority handling between UEs by means of dynamic scheduling    -   MBMS identification    -   Transport format selection    -   Padding

The PHY layer 1 d-20 or 1 d-25 may channel-code and modulate upper layerdata into OFDM symbols and transmit the OFDM symbols through a radiochannel, or demodulate OFDM symbols received through a radio channel andchannel-decode and deliver the OFDM symbols to an upper layer.

FIG. 1E is a diagram for describing a procedure of determining that a UE1 e-01 in an RRC idle mode RRC_IDLE or RRC inactive mode RRC_INACTIVE islocated in a certain coverage area, according to an embodiment of thedisclosure.

Hereinafter, for convenience of descriptions, an example in which the UE1 e-01 that was operating in an LTE system is located in a coverage areaof an NR system is described, but the LTE system and the NR system areonly examples, and an embodiment of the disclosure may be applied toanother next-generation communication system. In particular, FIG. 1E isa diagram for describing a procedure of determining whether the UE 1e-01 in the RRC idle mode (RRC_IDLE) or RRC inactive mode (RRC_INACTIVE)in the LTE system is located in a coverage area providing a 5G service.

An LTE base station according to an embodiment of the disclosure maysignal whether 5G capability is supported to the UE 1 e-01, as systeminformation. In other words, the LTE base station may signal anindicator of whether NG-RAN E-UTRA-NR dual connectivity ((NG)EN-DC) issupported for each public land mobile network (PLMN) to the UE 1 e-01,as system information. The UE 1 e-01 may determine whether the UE 1 e-01is located in a coverage area supporting 5G capability, based on theindicator included in the system information, and accordingly, the UE 1e-01 may display a 5G icon by transmitting an indicator indicatingwhether 5G is supported to an upper layer.

Referring to FIG. 1E, the UE 1 e-01 may establish an RRC connection withan evolved universal telecommunications system (UMTS) terrestrial radioaccess (EUTRA) cell 1 e-02 and thus be in an RRC connected mode(RRC_CONNECTED), in operation 1 e-05.

In operation 1 e-10, when there is no data transmission/reception due toa certain reason or for a certain period of time, the EUTRA cell 1 e-02may transmit an RRC connection release message (RRCConnectionRelease) tothe UE 1 e-01. In operation 1 e-10, the RRC connection release messagemay include RRC inactive configuration information (rrc_InactiveConfig).

In operation 1 e-15, when the RRC connection release message includesthe RRC inactive configuration information, the UE 1 e-01 may transitionto the RRC inactive mode. When the RRC connection release message doesnot include the RRC inactive configuration information, the UE 1 e-01may transition to the RRC idle mode. In other words, the UE 1 e-01 thatreceived the RRC connection release message may transition to the RRCinactive mode or RRC idle mode depending on whether the RRC inactiveconfiguration information is included in the RRC connection releasemessage.

In operation 1 e-20, the UE 1 e-01 in the RRC idle mode or RRC inactivemode may select a PLMN. The UE 1 e-01 may select the PLMN via a seriesof following processes.

-   -   The UE 1 e-01 may scan all radio frequency (RF) channels with        respect to E-UTRA bands depending on capability of the UE 1        e-01.    -   For each carrier, the UE 1 e-01 may find a cell having strongest        signal strength and receive system information from the cell.    -   When at least one PLMN identifier is receivable from the cell        having the strongest signal strength, the UE 1 e-01 may report        an upper layer (for example, NAS) that the at least one PLMN        identifier is a high quality PLMN. Here, when a measured        received signal received power (RSRP) value is equal to or        greater than −110 dBm, the UE 1 e-01 may report the upper layer        about the high quality PLMN, and when not, the UE 1 e-01 may        report the upper layer together with the RSRP value.    -   When the UE 1 e-01 supports E-UTRA connected to a 5G core (5GC)        with respect to a found PLMN, the UE 1 e-01 may also report a CN        type to the upper layer.

In operation 1 e-25, the UE 1 e-01 in the RRC idle mode or RRC inactivemode may perform a cell selection process. The cell selection processmay denote a process for the UE 1 e-01 to camp on a suitable cellassociated to the PLMN selected in operation 1 e-20. The suitable cellmay denote a cell satisfying following conditions.

-   -   When the cell is a part of either the selected PLMN, a        registered PLMN, or a PLMN of an equivalent PLMN list    -   When the cell is not barred according to information provided        from the upper layer    -   When the cell is a part of at least one Tracking Area (TA) that        is not a part of a list of “forbidden tracking areas for        roaming”, which belongs to the PLMN described above (The cell is        part of at least one TA that is not part of the list of        “forbidden tracking areas for roaming), which belongs to a PLMN        that fulfils the first bullet above)

In operation 1 e-25, the UE 1 e-01 in the RRC idle mode or RRC inactivemode may receive the system information to perform the cell selectionprocess. In operation 1 e-25, when the UE 1 e-01 receivedSystemInformationBlockType1, the UE 1 e-01 may use plmn-IdentityList,trackingAreaCode, and cellIdentity for the cell as received in acorresponding cellAccessRelatedInfoList containing the selected PLMN inoperation 1 e-20. In particular, the plmn-IdentityList may include atleast one PLMN-IdentityInfo, and the plmn-IdentityList including atleast one PLMN-IdentityInfo for each core type (for example, an evolvedpacket core (EPC) and/or 5GC) supported by an LTE cell may beconfigured. For example, PLMN-IdentityInfo of the LTE cell connected tothe EPC may be configured of plmn-IdentityList up to maxPLMN-r11. Forreference, maxPLMN-r11 may have a value of 6. Also, PLMN-IdentityInfo ofthe LTE cell connected to the 5GC may be configured of plmn-IdentityListup to maxPLMN-r11. Similarly, maxPLMN-r11 may have a value of 6. One LTEcell may be connected only to the EPC, only to the 5GC, or both to theEPC and the 5GC. plmn-IdentityList may have an ASN.1 structure below.

-   -   Referring to Table 1, at least one PLMN-IdentityInfo may be        configured for the LTE cell connected to the EPC, and each        PLMN-IdentityInfo may be configured of a plmn-Identity value and        cellReservedForOperatorUse.

TABLE 1 PLMN-IdentityList ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-IdentityInfo PLMN-IdentityInfo ::= SEQUENCE { plmn-IdentityPLMN-Identity, cellReservedForOperatorUse ENUMERATED {reserved,notReserved} }

-   -   Hereinafter, PLMN-IdentityInfo will be described with reference        to Table 2. At least one PLMN-IdentityInfo may be configured for        the LTE cell connected to the 5GC. Also, when a same        PLMN-Identity as the LTE connected to the EPC is used, each        PLMN-IdentityInfo may include a plmn index instead of the        PLMN-Identity value itself. For example, when the plmn index is        ‘1’, the plmn index may denote PLMN-Identity included in first        PLMN-IdentityInfo of the LTE cell connected to the EPC. When the        plmn index is ‘2’, the plmn index may denote PLMN-Identity        included in second PLMN-IdentityInfo of the LTE cell connected        to the EPC. Accordingly, because PLMN-IdentityInfo does not        include the same PLMN-Identity value, but includes plmn index,        signaling overhead may be reduced. When PLMN-Identity different        from the LTE cell connected to the EPC is to be broadcasted to        each PLMN-IdentityInfo, the PLMN-Identity value itself may be        included. In other words, the LTE cell may determine whether to        broadcast the PLMN-Identity or plmn index via a CHOICE        structure, and signal a result of the determination to the UE 1        e-01. Also, PLMN-IdentityInfo may include        cellReservedForOperatorUse for each PLMN.

TABLE 2 PLMN-IdentityInfo-r15 ::= SEQUENCE { plmn-Identity-5GC-r15CHOICE{ plmn-Identity-r15 PLMN-Identity, plmn-Index-r15 INTEGER(1..maxPLMN-r11) }, cellReservedForOperatorUse-r15 ENUMERATED {reserved,notReserved}, cellReservedForOperatorUse-CRS-r15 ENUMERATED {reserved,notReserved} }

In operation 1 e-25, the UE 1 e-01 may receiveSystemInformationBlockType2. In this case, in operation 1 e-30, the UE 1e-01 may determine whether to transmit, to an upper layer,upperLayerIndication including information that the UE 1 e-01 is withinthe coverage area providing the 5G service. In particular, theSystemInformationBlockType2 may include the upperLayerIndication aboutproviding of 5G capability for each PLMN in a same order as PLMNinformation (PLMN identity/plmn index) included in theSystemInformationBlockType1. A corresponding ASN.1 structure is asfollows.

-   -   PLMN-InfoList including at least one PLMN-Info may be        broadcasted in SystemInformationBlockType2.    -   Each PLMN-Info may be mapped in a same order of PLMN Identity or        plmn index broadcasted in SystemInformationBlockType1. In other        words, first PLMN-Info may be mapped to plmn-Identity of first        PLMN-IdentityInfo broadcasted in SystemInformationBlockType1.    -   Referring to Table 3, each PLMN-Info may include        upperLayerIndication indicator about whether a cell in a        corresponding PLMN provides 5G capability. When        upperLayerIndication is set to TRUE, the cell in the        corresponding PLMN may provide 5G capability. Otherwise, the        cell in the corresponding PLMN may not provide 5G capability.

TABLE 3 PLMN-InfoList-r15 ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-Info-r15 PLMN-Info-r15 ::= SEQUENCE { upperLayerIndication-r15ENUMERATED {true} OPTIONAL -- Need OR } -- ASN1STOP

When upperLayerIndication is set to TRUE with respect to the PLMNselected in operation 1 e-25 (or the selected PLMN identity), the UE 1e-01 in the RRC idle mode or RRC inactive mode may transmitupperLayerIndication to the upper layer in operation 1 e-30. Otherwise,the UE 1 e-01 may indicate that a corresponding field is absent (the UEshall to upper layers either forward upperLayerIndication, if presentfor the selected PLMN, or otherwise indicate absence of this field). TheupperLayerIndication may be an indicator notifying the upper layers thatthe UE 1 e-01 is in the coverage area providing the 5G service(upperLayerIndication is an indication to upper layers that the UE hasentered a coverage area that offers 5G capabilities). For reference,when the UE 1 e-01 transmits the upperLayerIndication to the upperlayer, the UE 1 e-01 may display a 5G icon on a display of the UE 1e-01.

FIG. 1F is a diagram for describing a procedure of determining whether aUE 1 f-01 supports a certain frequency band, according to an embodimentof the disclosure. Hereinafter, for convenience of description, anexample in which the UE 1 f-01 that is operating in an LTE system islocated in a coverage area providing NR capability is described, but theLTE system and an NR system are only examples, and an embodiment of thedisclosure may be applied to another next-generation communicationsystem. In detail, FIG. 1F is a diagram for describing a procedure inwhich the LTE system determines that the UE 1 f-01 in an RRC idle mode(RRC_IDLE) or RRC inactive mode (RRC_INACTIVE) is located in a coveragearea providing 5G capability and determines whether the UE 1 f-01supports an NR frequency band supporting (NG)EN-DC.

A EUTRA cell 1 f-02 according to an embodiment of the disclosure maysignal whether 5G capability is supported, as system information. Forexample, the EUTRA cell 1 f-02 may signal, to the UE 1 f-01, an NRfrequency band list supporting (NG)EN-DC for per PLMN, as the systeminformation. As described in the above embodiment of the disclosure, theUE 1 f-01 may determine whether the UE is located in the coverage areasupporting the 5G capability, based on an indicator included in thesystem information. Also, the UE 1 f-01 may display a 5G icon bytransmitting an indicator indicating the 5G capability to an upperlayer, based on whether at least one NR frequency band in the NRfrequency band list supporting (NG)EN-DC included in the systeminformation is supported.

Referring to FIG. 1F, the UE 1 f-01 may establish an RRC connection withthe EUTRA cell 1 f-02 and thus be in an RRC connected mode(RRC_CONNECTED), in operation 1 f-05.

In operation 1 f-10, when there is no data transmission/reception due toa certain reason or for a certain period of time, the EUTRA cell 1 f-02may transmit an RRC connection release message (RRCConnectionRelease) tothe UE 1 f-01. In operation 1 f-10, the RRC connection release messagemay include RRC inactive configuration information (rrc_InactiveConfig).In operation 1 f-15, when the RRC connection release message includesthe RRC inactive configuration information, the UE 1 f-01 may transitionto the RRC inactive mode. In operation 1 f-15, when the RRC connectionrelease message does not include the RRC inactive configurationinformation, the UE 1 f-01 may transition to the RRC idle mode. In otherwords, the UE 1 f-01 that received the RRC connection release messagemay transition to the RRC inactive mode or RRC idle mode depending onwhether the RRC inactive configuration information is included in theRRC connection release message.

In operation 1 f-20, the UE 1 f-01 in the RRC idle mode or RRC inactivemode may select a PLMN. The UE 1 f-01 may select the PLMN via a seriesof following processes.

-   -   The UE 1 f-01 may scan all RF channels with respect to E-UTRA        bands depending on capability of the UE 1 f-01.    -   For each carrier, the UE 1 f-01 may find a cell having strongest        signal strength and receive system information from the cell.    -   When at least one PLMN identifier is receivable from the cell        having the strongest signal strength, the UE 1 f-01 may report        an upper layer (for example, NAS) that the at least one PLMN        identifier is a high quality PLMN. Here, when a measured RSRP        value is equal to or greater than −110 dBm, the UE 1 f-01 may        report the upper layer about the high quality PLMN, and when        not, the UE 1 f-01 may report the upper layer together with the        RSRP value.    -   When the UE 1 f-01 supports E-UTRA connected to a 5GC with        respect to a found PLMN, the UE 1 f-01 may also report a CN type        to the upper layer.

In operation 1 f-25, the UE 1 f-01 in the RRC idle mode or RRC inactivemode may perform a cell selection process. The cell selection processmay denote a process for the UE 1 f-01 to camp on a suitable cellassociated to the PLMN selected in operation 1 f-20. The suitable cellmay denote a cell satisfying following conditions.

-   -   When the cell is a part of either the selected PLMN, a        registered PLMN, or a PLMN of an equivalent PLMN list    -   When the cell is not barred according to information recently        provided from the upper layer    -   When the cell is a part of at least one TA that is not a part of        a list of “forbidden tracking areas for roaming”, which belongs        to the PLMN described above (The cell is part of at least one TA        that is not part of the list of “forbidden tracking areas for        roaming), which belongs to a PLMN that fulfils the first bullet        above)

In operation 1 f-25, the UE 1 f-01 in the RRC idle mode or RRC inactivemode may receive the system information to perform the cell selectionprocess.

In operation 1 f-25, the UE 1 f-01 may receiveSystemInformationBlockType1. Here, when PLMN Identity or plmn indexmatching the PLMN selected in operation 1 f-20 is included incellAccessRelatedInfoList, plmn-IdentityList, trackingAreaCode, andcellIdentity included in cellAccessRelatedInfoList may be used. Inparticular, the plmn-IdentityList may include at least onePLMN-IdentityInfo, and the plmn-IdentityList including at least onePLMN-IdentityInfo for each core type (for example, an evolved packetcore (EPC) and/or 5GC) supported by an LTE cell may be configured. Forexample, PLMN-IdentityInfo of the LTE cell connected to the EPC may beconfigured of plmn-IdentityList up to maxPLMN-r11. For example,maxPLMN-r11 may have a value of 6. Alternatively, PLMN-IdentityInfo ofan LTE cell connected to EPC based on a newly defined constant value maybe configured of plmn-IdentityList up to maxPLMN-r16. Similarly,PLMN-IdentityInfo of the LTE cell connected to the 5GC may be configuredof plmn-IdentityList up to maxPLMN-r11. For example, maxPLMN-r11 mayhave a value of 6. Alternatively, PLMN-IdentityInfo of the LTE cellconnected to the 5GC based on a newly defined constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. One LTE cell may beconnected only to the EPC, only to the 5GC, or both to the EPC and the5GC. plmn-IdentityList may have an ASN.1 structure below.

-   -   Referring to Table 4, at least one PLMN-IdentityInfo may be        configured for the LTE cell connected to the EPC, and each        PLMN-IdentityInfo may be configured of a plmn-Identity value and        cellReservedForOperatorUse.

TABLE 4 PLMN-IdentityList ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-IdentityInfo PLMN-IdentityInfo ::= SEQUENCE { plmn-IdentityPLMN-Identity, cellReservedForOperatorUse ENUMERATED {reserved,notReserved} }

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the 5GC, and each PLMN-IdentityInfo may        include a plmn index when a same Plmn-Identity as the LTE cell        connected to the EPC is used. For example, when the plmn index        is ‘1’, the plmn index may denote PLMN-Identity included in        first PLMN-IdentityInfo of the LTE cell connected to the EPC.        Also, when the plmn index is ‘2’, the plmn index may denote        PLMN-Identity included in second PLMN-IdentityInfo of the LTE        cell connected to the EPC. Accordingly, PLMN-IdentityInfo does        not include the same PLMN-Identity value, but includes plmn        index, and thus signaling overhead may be reduced. When        PLMN-Identity different from the LTE cell connected to the EPC        is to be broadcasted to each PLMN-IdentityInfo, the        PLMN-Identity value itself may be included. In other words, the        LTE cell may determine whether to broadcast the PLMN-Identity or        plmn index via a CHOICE structure, and signal a result of the        determination to the UE 1 f-01. Also, PLMN-IdentityInfo may        include cellReservedForOperatorUse for each PLMN Identity.

TABLE 5 PLMN-IdentityInfo-r15 ::= SEQUENCE { plmn-Identity-5GC-r15CHOICE{ plmn-Identity-r15 PLMN-Identity, plmn-Index-r15 INTEGER(1..maxPLMN-r11) }, cellReservedForOperatorUse-r15 ENUMERATED {reserved,notReserved}, cellReservedForOperatorUse-CRS-r15 ENUMERATED {reserved,notReserved} }

In operation 1 f-25, the EUTRA cell 1 f-02 may broadcast the NRfrequency band list supporting (NG)EN-DC per PLMN, as the systeminformation. For example, the NR frequency band list supporting(NG)EN-DC per PLMN may be broadcasted from SystemInformationBlockType1,SystemInformationBlockType2, SystemInformationBlockType5,SystemInformationBlockType24, or new SystemInformationBlockType (forexample, SystemInformationBlockType27). In the disclosure, the NRfrequency band list supporting (NG)EN-DC per PLMN may be broadcasted ina same order as PLMN-Identity/plmn index included in a plmn-IdentityListfield of SystemInformationBlockType1. In other words, theplmn-IdentityList field does not need to additionally include aPLMN-Identity/plmn-index value itself. For example, the ASN.1 structuremay have a following structure.

-   -   Because the NR frequency band list per PLMN is broadcasted via        the system information in the same order as plmn-Identity        included in the plmn-IdentityList field of        SystemInformationBlockType1, separate plmn identity/plmn index        may not be included.    -   Some plmn-Identity among plmn-Identity included in        SystemInformationBlockType1 may not support the NR frequency        band list supporting (NG)EN-DC. Accordingly, the NR frequency        band list may be broadcasted from 0. In other words, when 0 is        broadcasted for the NR frequency band list, a plmn corresponding        to the plmn-Identity may denote that the NR frequency band list        supporting (NG)EN-DC is not supported. Obviously, when there is        no NR frequency band list supporting (NG)EN-DC in some        plmn-Identity, the NR frequency band list may not be        broadcasted.    -   Some plmn-Identity among plmn-Identity included in        SystemInformationBlockType1 may include a plurality of NR        frequency band lists supporting (NG)EN-DC. In this case, the NR        frequency band lists including NR frequency bands up to a        specific constant value (constant To Be Determined (TBD)) may be        broadcasted.    -   Each NR frequency band supporting (NG)EN-DC may be indicated as        FreqBandIndicatorNR, an absolute radio frequency channel number,        or a carrier frequency. This may be represented as Table 6        below.

TABLE 6 -- ASN1START  x = 1, 2, 5, 24, or 27 (new)SystemInformationBlockTypex ::= SEQUENCE { NRFreqBandENDC-List SEQUENCE(SIZE (1..maxPLMN-r11)) OF FreqBandNR-List . . . } FreqBandNR-List ::=SEQUENCE {SIZE (0..constantTBD)} OF FreqBandinIndicatorNR -- ASN1STOP

NRFreqBandENDC-List

The NR frequency bands supporting EN-DC per PLMN, listed in the sameorder as the PLMN(s) listed across the plmn-IdentityList fields inSystemInformationBlockType1.

The broadcasting of the NR frequency band list supporting (NG)EN-DC perPLMN via the system information, according to an embodiment of thedisclosure may be in a following form.

-   -   For PLMN-Identity 1, an NR frequency band list supporting        (NG)EN-DC may be broadcasted as 10, 20, 30. 10, 20, 30 may        denote FreqBandIndicatorNR.    -   For PLMN-Identity 2, an NR frequency band list supporting        (NG)EN-DC may be broadcasted as 100, 200, 300. 100, 200, 300 may        denote FreqBandIndicatorNR.    -   For PLMN-Identity 3, there may be no NR frequency band        supporting (NG)EN-DC. Here, 0 may be broadcasted or nothing may        be broadcasted. This may be represented as Table 7 below.

TABLE 7 SystemInformationBlockType1 PLMN-IdentityList PLMN-Identity 1PLMN-Identity 2 PLMN-Identity 3 SystemInformationBlockType x (x is 1, 2,5, 24, or 27) NRFreqBandENCD-List 10, 20, 30 100, 200, 300 0In the above table, the three NRFreqBandENCD-List values representFreqBandNR-List per PLMN, and PLMN-Identity 1 corresponds to the firstlist of NRFreqBandENCD-List values (10, 20, 30), PLMN-Identity 2corresponds to the second list of NRFreqBandENCD-List values (100, 200,300), and PLMN-Identity 3 corresponds to the third list ofNRFreqBandENCD-List values (0).

In operation 1 f-25, the UE 1 f-01 may receive the system informationincluding the NR frequency band list supporting (NG)EN-DC per PLMN, asdescribed above. Here, the UE 1 f-01 may receiveSystemInformationBlockType2. In particular, theSystemInformationBlockType2 may include an indicator(upperLayerIndication) about providing of 5G capability for each PLMN ina same order as PLMN information (PLMN identity/plmn index) included inthe SystemInformationBlockType1. An ASN.1 structure is as follows.

-   -   PLMN-InfoList including at least one PLMN-Info may be        broadcasted in SystemInformationBlockType2.    -   Each PLMN-Info may be mapped in a same order of PLMN        Identity/plmn index broadcasted in SystemInformationBlockType1.        In other words, first PLMN-Info may be mapped to plmn-Identity        of first PLMN-IdentityInfo broadcasted in        SystemInformationBlockType1.    -   Each PLMN-Info may include upperLayerIndication indicator about        whether a corresponding PLMN provides 5G capability. When        upperLayerIndication is set to TRUE, the cell in the        corresponding PLMN may provide 5G capability. Otherwise, the        cell in the corresponding PLMN may not provide 5G capability.        For reference, upperLayerIndication may be set to TRUE only when        the NR frequency band supporting (NG)EN-DC is present.

TABLE 8 PLMN-InfoList-r15 ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-Info-r15 PLMN-Info-r15 ::= SEQUENCE { upperLayerIndication-r15ENUMERATED {true} OPTIONAL -- Need OR } -- ASN1STOP

In operation 1 f-30, the UE 1 f-01 may transmit the upperLayerIndicationto the upper layer when the upperLayerIndication is set to TRUE for thePLMN selected in operation 1 f-20 and at least one NR frequency band issupported in the NR frequency band list supporting (NG)EN-DC for theselected PLMN. The upperLayerIndication may refer to an indicator forindicating the upper layer that the UE 1 f-01 has entered or is locatedin the coverage area providing 5G capability and the at least one NRfrequency band is supported in the NR frequency band list supported bythe cell for the selected PLMN. Otherwise, the UE 1 f-01 may indicate,to the upper layer, absence of the upperLayerIndication. In other words,the UE 1 f-01 may indicate, to the upper layer, the absence of theupperLayerIndication when there is no upperLayerIndication for theselected PLMN, FALSE is set, and/or at least one NR frequency band isnot supported among the NR frequency band list for the selected PLMN.For reference, when the UE 1 f-01 transmits the upperLayerIndication tothe upper layer, the UE 1 f-01 may display a 5G icon on a display of theUE 1 f-01.

In operation 1 f-30, the UE 1 f-01 may transmit, to the upper layer, theupperLayerIndication including information that the upperLayerIndicationfor the PLMN registered in operation 1 f-20 or a PLMN belonging to anequivalent PLMN list is set to TRUE and that at least one NR frequencyband is supported in the NR frequency band list supported by the cellfor the corresponding PLMN. Otherwise, the UE 1 f-01 may indicate, tothe upper layer, absence of the upperLayerIndication.

In operation 1 f-30, the UE 1 f-01 may transmit the upperLayerIndicationto the upper layer when at least one NR frequency band is supported inthe NR frequency band list supporting (NG)EN-DC for the selected PLMN,regardless of the upperLayerIndication being set to TRUE. In otherwords, the upperLayerIndication may denote an indicator for indicatingthe upper layer that the at least one NR frequency band is supported inthe NR frequency band list for (NG)EN-DC supported by the cell for theselected PLMN. Otherwise, the UE 1 f-01 may indicate, to the upperlayer, absence of the upperLayerIndication. For reference, theupperLayerIndication may be used distinguishably from existingupperLayerIndication by introducing a new indicator different from theexisting upperLayerIndication.

FIG. 1G is a diagram for describing a procedure of determining whether aUE 1 g-01 supports a certain frequency band, according to an embodimentof the disclosure. Hereinafter, for convenience of description, anexample in which the UE 1 g-01 that was operating in an LTE system islocated in a coverage area of an NR system is described, but the LTEsystem and the NR system are only examples, and an embodiment of thedisclosure may be applied to another next-generation communicationsystem. In detail, FIG. 1G is a diagram for describing a procedure ofdetermining that the UE 1 g-01 in an RRC idle mode (RRC_IDLE) or RRCinactive mode (RRC_INACTIVE) is located in a certain coverage area anddetermining whether a serving cell supports an NR frequency bandsupporting (NG)EN-DC.

An LTE base station according to an embodiment of the disclosure maysignal whether 5G capability is supported, as system information. Forexample, an LTE base station may signal, to the UE 1 g-01, an NRfrequency band list supporting (NG)EN-DC for per PLMN, as the systeminformation. Because an NR frequency band list may be the same per PLMNaccording to an embodiment of the disclosure, when an NR frequency bandlist is included for a previous PLMN, a previous PLMN index or previousplmn-Identity may be included for a PLMN supporting the same NRfrequency band list. Accordingly, signaling overhead may be reducedbecause redundant NR frequency band list is not included in systeminformation with respect to at least one PLMN. As described in the aboveembodiment of the disclosure, the UE 1 g-01 may determine whether the UE1 g-01 has entered or is located in a coverage area supporting 5Gcapability, based on an indicator included in the system information.Also, the UE 1 g-01 may display a 5G icon by transmitting an indicatorindicating the 5G capability to an upper layer, based on whether atleast one NR frequency band in the NR frequency band list supporting(NG)EN-DC included in the system information is supported.

Referring to FIG. 1G, the UE 1 g-01 may establish an RRC connection witha EUTRA cell 1 g-02 and thus be in an RRC connected mode(RRC_CONNECTED), in operation 1 g-05.

In operation 1 g-10, when there is no data transmission/reception due toa certain reason or for a certain period of time, the EUTRA cell 1 g-02may transmit an RRC connection release message (RRCConnectionRelease) tothe UE 1 g-01. In operation 1 g-10, the RRC connection release messagemay include RRC inactive configuration information (rrc_InactiveConfig).

In operation 1 g-15, when the RRC connection release message includesthe RRC inactive configuration information, the UE 1 g-01 may transitionto the RRC inactive mode. When the RRC connection release message doesnot include the RRC inactive configuration information, the UE 1 g-01may transition to the RRC idle mode. In other words, the UE 1 g-01 thatreceived the RRC connection release message may transition to the RRCinactive mode or RRC idle mode depending on whether the RRC inactiveconfiguration information is included.

In operation 1 g-20, the UE 1 g-01 in the RRC idle mode or RRC inactivemode may select a PLMN. The UE 1 g-01 may select the PLMN via a seriesof following processes.

-   -   The UE 1 g-01 may scan all RF channels with respect to E-UTRA        bands depending on capability of the UE 1 g-01.    -   For each carrier, the UE 1 g-01 may find a cell having strongest        signal strength and receive system information from the cell.    -   When at least one PLMN identifier is receivable from the cell        having the strongest signal strength, the UE 1 g-01 may report        an upper layer (for example, NAS) that the at least one PLMN        identifier is a high quality PLMN. Here, when a measured RSRP        value is equal to or greater than −110 dBm, the UE 1 g-01 may        report the upper layer about the high quality PLMN, and when        not, the UE 1 g-01 may report the upper layer together with the        RSRP value.    -   When the UE 1 g-01 supports E-UTRA connected to a 5GC with        respect to a found PLMN, the UE 1 g-01 may also report a CN type        to the upper layer.

In operation 1 g-25, the UE 1 g-01 in the RRC idle mode or RRC inactivemode may perform a cell selection process. The cell selection processmay denote a process for the UE 1 g-01 to camp on a suitable cellassociated to the PLMN selected in operation 1 g-20. The suitable cellmay denote a cell satisfying following conditions.

-   -   When the cell is a part of either the selected PLMN, a        registered PLMN, or a PLMN of an equivalent PLMN list    -   When the cell is not barred according to information provided        from the upper layer    -   When the cell is a part of at least one TA that is not a part of        a list of “forbidden tracking areas for roaming”, which belongs        to the PLMN described above (The cell is part of at least one TA        that is not part of the list of “forbidden tracking areas for        roaming), which belongs to a PLMN that fulfills the first bullet        above)

In operation 1 g-25, the UE 1 g-01 in the RRC idle mode or RRC inactivemode may receive the system information to perform the cell selectionprocess. In operation 1 g-25, when the UE 1 g-01 receivedSystemInformationBlockType1, a PLMN identity or plmn index correspondingto the PLMN selected in operation 1 g-20 may be included incellAccessRelatedInfoList. In this case, plmn-IdentityList,trackingAreaCode, and cellIdentity for a cell as received in thecorresponding cellAccessRelatedInfoList containing the selected PLMN maybe used. In particular, the plmn-IdentityList may include at least onePLMN-IdentityInfo, and the plmn-IdentityList including at least onePLMN-IdentityInfo for each core type (for example, an evolved packetcore (EPC) and/or 5GC) supported by an LTE cell may be configured. Forexample, PLMN-IdentityInfo of the LTE cell connected to the EPC may beconfigured of plmn-IdentityList up to maxPLMN-r11. For example,maxPLMN-r11 may have a value of 6. Alternatively, PLMN-IdentityInfo ofan LTE cell connected to EPC by defining a new constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. Similarly,PLMN-IdentityInfo of the LTE cell connected to the 5GC may be configuredof plmn-IdentityList up to maxPLMN-r11. For example, maxPLMN-r11 mayhave a value of 6. Alternatively, PLMN-IdentityInfo of the LTE cellconnected to the 5GC based on a newly defined constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. One LTE cell may beconnected only to the EPC, only to the 5GC, or both to the EPC and the5GC. plmn-IdentityList may have an ASN.1 structure below.

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the EPC, and each PLMN-IdentityInfo may be        configured of a plmn-Identity value and        cellReservedForOperatorUse. This may be represented as Table 9        below.

TABLE 9 PLMN-IdentityList ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-IdentityInfo PLMN-IdentityInfo ::= SEQUENCE { plmn-IdentityPLMN-Identity, cellReservedForOperatorUse ENUMERATED {reserved,notReserved} }

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the 5GC, and each PLMN-IdentityInfo may        include a plmn index when a same Plmn-Identity as the LTE cell        connected to the EPC is used. For example, when the plmn index        is ‘1’, the plmn index may denote PLMN-Identity included in        first PLMN-IdentityInfo of the LTE cell connected to the EPC.        Also, when the plmn index is ‘2’, the plmn index may denote        PLMN-Identity included in second PLMN-IdentityInfo of the LTE        cell connected to the EPC. In other words, PLMN-IdentityInfo        does not include the same PLMN-Identity value, but includes plmn        index, and thus signaling overhead may be reduced. When        PLMN-Identity different from the LTE cell connected to the EPC        is to be broadcasted to each PLMN-IdentityInfo, the        PLMN-Identity value itself may be included. In other words, the        LTE cell may determine whether to broadcast the PLMN-Identity or        plmn index via a CHOICE structure, and signal a result of the        determination to the UE 1 g-01. Also, PLMN-IdentityInfo may        include cellReservedForOperatorUse for each PLMN. This may be        represented as Table 10 below.

TABLE 10 PLMN-IdentityInfo-r15 ::= SEQUENCE { plmn-Identity-5GC-r15CHOICE{ plmn-Identity-r15 PLMN-Identity, plmn-Index-r15 INTEGER(1..maxPLMN-r11) }, cellReservedForOperatorUse-r15 ENUMERATED {reserved,notReserved}, cellReservedForOperatorUse-CRS-r15 ENUMERATED {reserved,notReserved} }

In operation 1 g-25, the EUTRA cell 1 g-02 may broadcast the NRfrequency band list supporting (NG)EN-DC per PLMN, as the systeminformation. For example, the NR frequency band list supporting(NG)EN-DC per PLMN may be broadcasted from SystemInformationBlockType1,SystemInformationBlockType2, SystemInformationBlockType5,SystemInformationBlockType24, or new SystemInformationBlockType (forexample, SystemInformationBlockType27). According to an embodiment ofthe disclosure, when a specific PLMN includes an NR frequency band listsuch that the system information does not include a redundant NRfrequency band list for at least one PLMN, another PLMN supporting thesame NR frequency band list may indicate that the same NR frequency bandlist is supported by using a specific PLMN identity or a PLMN indexindicating the specific PLMN identity. In this case, signaling overheadmay be reduced because the redundant frequency band list is not includedin the system information per PLMN.

-   -   The NR frequency band list per PLMN may be broadcasted in a same        order as PLMN-Identity/plmn index included in a        plmn-IdentityList field of SystemInformationBlockType1.    -   Some plmn-Identity among plmn-Identity of        SystemInformationBlockType1 may not support the NR frequency        band list supporting (NG)EN-DC. Accordingly, the NR frequency        band list may be broadcasted from 0. In other words, when 0 is        broadcasted for the NR frequency band list, a plmn corresponding        to the plmn-Identity may denote that the NR frequency band list        supporting (NG)EN-DC is not supported. Obviously, when there is        no NR frequency band list supporting (NG)EN-DC in some        plmn-Identity, the NR frequency band list may not be        broadcasted.    -   Some plmn-Identity among plmn-Identity included in        SystemInformationBlockType1 may include one or a plurality of NR        frequency band lists supporting (NG)EN-DC. In this case, the NR        frequency band lists including NR frequency bands up to a        maximum specific constant value (constant TBD) may be        broadcasted.    -   When the NR frequency band list supporting (NG)EN-DC is included        in a previous PLMN and the same NR frequency band list for        (NG)EN-DC is supported in a current PLMN,        SystemInformationBlockTypex may not include the NR frequency        band list but may include a previous PLMN index or PLMN        identity. In other words, the NR frequency band list may be        indicated via a choice structure.    -   Each NR frequency band may be indicated by FreqBandIndicatorNR,        an absolute radio frequency channel number, or a carrier        frequency.

For example, the broadcasting of the NR frequency band list supporting(NG)EN-DC per PLMN via the system information, according to anembodiment of the disclosure may be in a form of Table 11 below.

TABLE 11 SystemInformationBlockType1 PLMN-IdentityList PLMN-Identity 1PLMN-Identity 2 PLMN-Identity 3 SystemInformationBlockType x (x is 1, 2,5, 24, or 27) NRFreqBandENCD- FreqBandNR-List 10, 20, 30 ListPLMN-IdentityIndex 1 (PLMN-Identity 1) (PLMN-Identity) FreqBandNR-List 0

In the above table, PLMN-Identity 1 corresponds to the first list ofNRFreqBandENCD-List values (10, 20, 30), PLMN-Identity 2 corresponds tothe second list of NRFreqBandENCD-List values (1, or PLMN-Identity 1),and PLMN-Identity 3 corresponds to the third list of NRFreqBandENCD-Listvalues (0).

-   -   For PLMN-Identity 1, an NR frequency band list supporting        (NG)EN-DC may be broadcasted as 10, 20, 30. 10, 20, 30 may        denote FreqBandIndicatorNR.    -   For PLMN-Identity 2, because the NR frequency band list        supporting (NG)EN-DC is the same as the NR frequency band list        supported by PLMN-Identity 1, PLMN-Identity 2 may not include        the NR frequency band list, but may include PLMN-Identity 1 or        plmn index ‘1’ indicating PLMN-Identity.—Accordingly,        PLMN-Identity 2 may indicate that the NR frequency band list        supporting (NG)EN-DC is 10, 20, 30.    -   For PLMN-Identity 3, there may be no NR frequency band        supporting (NG)EN-DC. Here, 0 may be broadcasted or nothing may        be broadcasted.

In operation 1 g-25, the UE 1 g-01 may receive the system informationincluding the NR frequency band list supporting (NG)EN-DC per PLMN, asdescribed above. Here, the UE 1 g-01 may receiveSystemInformationBlockType2. In particular, theSystemInformationBlockType2 may include an indicator(upperLayerIndication) about providing of 5G capability for each PLMN ina same order as PLMN information (PLMN identity/plmn index) included inthe SystemInformationBlockType1. An ASN.1 structure is as follows.

-   -   PLMN-InfoList including at least one PLMN-Info may be        broadcasted in SystemInformationBlockType2.    -   Each PLMN-Info may be mapped in a same order of PLMN Identity        broadcasted in SystemInformationBlockType1. In other words,        first PLMN-Info may be mapped to plmn-Identity of first        PLMN-IdentityInfo broadcasted in SystemInformationBlockType1.    -   Each PLMN-Info may include upperLayerIndication indicator about        whether a corresponding PLMN provides 5G capability. When        upperLayerIndication is set to TRUE, the corresponding PLMN may        provide 5G capability. Otherwise, the corresponding PLMN may not        provide 5G capability. For reference, upperLayerIndication may        be set to TRUE only when the NR frequency band supporting        (NG)EN-DC is present. This may be represented as Table 12 below.

TABLE 12 PLMN-InfoList-r15 ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-Info-r15 PLMN-Info-r15 ::= SEQUENCE { upperLayerIndication-r15ENUMERATED {true} OPTIONAL -- Need OR } -- ASN1STOP

In operation 1 g-30, the UE 1 g-01 may transmit the upperLayerIndicationto the upper layer when the upperLayerIndication is set to TRUE for thePLMN selected in operation 1 g-20 and at least one NR frequency band issupported in the NR frequency band list supporting (NG)EN-DC for theselected PLMN. In other words, the upperLayerIndication may refer to anindicator for indicating the upper layer that the UE 1 g-01 has enteredor is located in the coverage area providing 5G capability and the atleast one NR frequency band is supported in the NR frequency band listfor (NG)EN-DC supported by the cell for the selected PLMN. Otherwise,the UE 1 g-01 may indicate, to the upper layer, absence of theupperLayerIndication. In other words, the UE 1 g-01 may indicate, to theupper layer, the absence of the upperLayerIndication when there is noupperLayerIndication for the selected PLMN, FALSE is set, and/or atleast one NR frequency band is not supported among the NR frequency bandlist for (NG)EN-DC for the selected PLMN. For reference, when the UE 1g-01 transmits the upperLayerIndication to the upper layer, the UE 1g-01 may display a 5G icon on a display of the UE 1 g-01.

In operation 1 g-30, the UE 1 g-01 may transmit, to the upper layer, theupperLayerIndication including information that the upperLayerIndicationfor the PLMN registered in operation 1 g-20 or a PLMN belonging to anequivalent PLMN list is set to TRUE and that at least one NR frequencyband is supported in the NR frequency band list for (NG)EN-DC withrespect to the corresponding PLMN. Otherwise, the UE 1 g-01 mayindicate, to the upper layer, absence of the upperLayerIndication.

In operation 1 g-30, the UE 1 g-01 may transmit the upperLayerIndicationto the upper layer when at least one NR frequency band is supported inthe NR frequency band list supporting (NG)EN-DC for the selected PLMN,regardless of the upperLayerIndication being set to TRUE. In otherwords, the upperLayerIndication may denote an indicator for indicatingthe upper layer that the at least one NR frequency band is supported inthe NR frequency band list for (NG)EN-DC supported by the cell for theselected PLMN. Otherwise, the UE 1 g-01 may indicate, to the upperlayer, absence of the upperLayerIndication. For reference, theupperLayerIndication may be used distinguishably from existingupperLayerIndication by introducing a new indicator different from theexisting upperLayerIndication.

FIG. 1H is a diagram for describing a procedure of determining whether aUE 1 h-01 supports a certain NR frequency band, according to anembodiment of the disclosure. Hereinafter, for convenience ofdescription, an example in which the UE 1 h-01 that was operating in anLTE system is located in a coverage area of an NR system is described,but the LTE system and the NR system are only examples, and anembodiment of the disclosure may be applied to another next-generationcommunication system. In detail, FIG. 1H is a diagram for describing aprocedure of determining that the UE 1 h-01 in an RRC idle mode(RRC_IDLE) or RRC inactive mode (RRC_INACTIVE) is located in a coveragearea providing 5G capability and determining whether a serving cellsupports an NR frequency band supporting (NG)EN-DC.

An LTE base station according to an embodiment of the disclosure maysignal whether 5G capability is supported, as system information. Forexample, the LTE base station may signal, to the UE 1 h-01, a NRfrequency band list supporting (NG)EN-DC for each PLMN list, as thesystem information. According to an embodiment of the disclosure, the NRfrequency band list may be the same per PLMN, and thus one NR frequencyband list may be broadcasted for a plurality of PLMNs, via the systeminformation. Signaling overhead may be reduced because redundant NRfrequency band list is not included in the system information withrespect to at least one PLMN. As described in the above embodiment ofthe disclosure, the UE 1 h-01 may determine whether the UE 1 h-01 hasentered or is located in a coverage area supporting 5G capability, basedon an indicator included in the system information. Also, the UE 1 h-01may display a 5G icon by transmitting an indicator indicating the 5Gcapability to an upper layer, based on whether at least one NR frequencyband in the NR frequency band list supporting (NG)EN-DC included in thesystem information is supported.

Referring to FIG. 1H, the UE 1 h-01 may establish an RRC connection witha EUTRA cell 1 h-02 and thus be in an RRC connected mode(RRC_CONNECTED), in operation 1 h-05.

In operation 1 h-10, when there is no data transmission/reception due toa certain reason or for a certain period of time, the EUTRA cell 1 h-02may transmit an RRC connection release message (RRCConnectionRelease) tothe UE 1 h-01. In operation 1 h-10, the RRC connection release messagemay include RRC inactive configuration information (rrc_InactiveConfig).

In operation 1 h-15, when the RRC connection release message includesthe RRC inactive configuration information, the UE 1 h-01 may transitionto the RRC inactive mode. When the RRC connection release message doesnot include the RRC inactive configuration information, the UE 1 h-01may transition to the RRC idle mode. In other words, the UE 1 h-01 thatreceived the RRC connection release message may transition to the RRCinactive mode or RRC idle mode depending on whether the RRC inactiveconfiguration information is included.

In operation 1 h-20, the UE 1 h-01 in the RRC idle mode or RRC inactivemode may select a PLMN. The UE 1 h-01 may select the PLMN via a seriesof following processes.

-   -   The UE 1 h-01 may scan all RF channels with respect to E-UTRA        bands depending on capability of the UE 1 h-01.    -   For each carrier, the UE 1 h-01 may find a cell having strongest        signal strength and receive system information from the cell.    -   When at least one PLMN identifier is receivable from the cell        having the strongest signal strength, the UE 1 h-01 may report        an upper layer (for example, NAS) that the at least one PLMN        identifier is a high quality PLMN. Here, when a measured RSRP        value is equal to or greater than −110 dBm, the UE 1 h-01 may        report the upper layer about the high quality PLMN, and when        not, the UE 1 h-01 may report the upper layer together with the        RSRP value.    -   When the UE 1 h-01 supports E-UTRA connected to a 5GC with        respect to a found PLMN, the UE 1 h-01 may also report a CN type        to the upper layer.

In operation 1 h-25, the UE 1 h-01 in the RRC idle mode or RRC inactivemode may perform a cell selection process. The cell selection processmay denote a process for the UE 1 h-01 to camp on a suitable cellassociated to the PLMN selected in operation 1 h-20. The suitable cellmay denote a cell satisfying following conditions.

-   -   When the cell is a part of either the selected PLMN, a        registered PLMN, or a PLMN of an equivalent PLMN list    -   When the cell is not barred according to information provided        from the upper layer    -   When the cell is a part of at least one TA that is not a part of        a list of “forbidden tracking areas for roaming”, which belongs        to the PLMN described above (The cell is part of at least one TA        that is not part of the list of “forbidden tracking areas for        roaming), which belongs to a PLMN that fulfils the first bullet        above)

In operation 1 h-25, the UE 1 h-01 in the RRC idle mode or RRC inactivemode may receive the system information to perform the cell selectionprocess. In operation 1 h-25, when the UE 1 h-01 receivedSystemInformationBlockType1, a PLMN identity/plmn index corresponding tothe PLMN selected in operation 1 h-20 may be included incellAccessRelatedInfoList. In this case, plmn-IdentityList,trackingAreaCode, and cellIdentity for a cell as received in thecorresponding cellAccessRelatedInfoList containing the selected PLMN maybe used. In particular, the plmn-IdentityList may include at least onePLMN-IdentityInfo, and the plmn-IdentityList including at least onePLMN-IdentityInfo for each core type (for example, an evolved packetcore (EPC) and/or 5GC) supported by an LTE cell may be configured. Forexample, PLMN-IdentityInfo of the LTE cell connected to the EPC may beconfigured of plmn-IdentityList up to maxPLMN-r11. For example,maxPLMN-r11 may have a value of 6. Alternatively, PLMN-IdentityInfo ofan LTE cell connected to EPC by defining a new constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. Similarly,PLMN-IdentityInfo of the LTE cell connected to the 5GC may be configuredof plmn-IdentityList up to maxPLMN-r11. For example, maxPLMN-r11 mayhave a value of 6. Alternatively, PLMN-IdentityInfo of the LTE cellconnected to the 5GC based on a newly defined constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. One LTE cell may beconnected only to the EPC, only to the 5GC, or both to the EPC and the5GC. The plmn-IdentityList may have an ASN.1 structure below.

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the EPC, and each PLMN-IdentityInfo may be        configured of a plmn-Identity value and        cellReservedForOperatorUse. This may be represented as Table 13        below.

TABLE 13 PLMN-IdentityList ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-IdentityInfo PLMN-IdentityInfo ::= SEQUENCE { plmn-IdentityPLMN-Identity, cellReservedForOperatorUse ENUMERATED {reserved,notReserved} }

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the 5GC, and each PLMN-IdentityInfo may        include a plmn index when a same Plmn-Identity as the LTE cell        connected to the EPC is used. For example, when the plmn index        is ‘1’, the plmn index may denote PLMN-Identity included in        first PLMN-IdentityInfo of the LTE cell connected to the EPC.        Also, when the plmn index is ‘2’, the plmn index may denote        PLMN-Identity included in second PLMN-IdentityInfo of the LTE        cell connected to the EPC. In other words, PLMN-IdentityInfo        does not include the same PLMN-Identity value, but includes plmn        index, and thus signaling overhead may be reduced. When        PLMN-Identity different from the LTE cell connected to the EPC        is to be broadcasted to each PLMN-IdentityInfo, the        PLMN-Identity value itself may be included. In other words, the        LTE cell may determine whether to broadcast the PLMN-Identity or        plmn index via a CHOICE structure, and signal a result of the        determination to the UE 1 h-01. Also, PLMN-IdentityInfo may        include cellReservedForOperatorUse for each PLMN.

In operation 1 h-25, the EUTRA cell 1 h-02 may broadcast the NRfrequency band list supporting (NG)EN-DC per PLMN list, as the systeminformation. For example, the NR frequency band list supporting(NG)EN-DC per PLMN list may be broadcasted fromSystemInformationBlockType1, SystemInformationBlockType2,SystemInformationBlockType5, SystemInformationBlockType24, or newSystemInformationBlockType (for example, SystemInformationBlockType27).In an embodiment of the disclosure, in order for the system informationnot to include the redundant NR frequency band list for at least onePLMN, plmn-IdentityList or plmn-IdentityIndex List may be included forat least one PLMN supporting the same NR frequency band list, and the NRfrequency band list mapped thereto may be broadcasted via the systeminformation. In this case, signaling overhead may be reduced because theredundant frequency band list is not included in the system informationper PLMN. For example, the ASN.1 structure may have a followingstructure.

-   -   When the NR frequency band lists supporting (NG)EN-DC are the        same for the at least one PLMN, the NR frequency band list for        same PLMN-IdentityIndexList or PLMN-IdentityList may be        broadcasted.    -   Some plmn-Identity among plmn-Identity included in        SystemInformationBlockType1 may not support the NR frequency        band list supporting (NG)EN-DC. Accordingly, the NR frequency        band list may be configured from 0. In other words, when 0 is        broadcasted for the NR frequency band list, a plmn corresponding        to the plmn-Identity may denote that the NR frequency band list        supporting (NG)EN-DC is not supported. Obviously, when a        specific PLMN identity does not include the NR frequency band        list, a corresponding PLMN may indicate that the NR frequency        band list supporting (NG)EN-DC is not supported.    -   At least one NR frequency band supporting (NG)EN-DC may be        present in PLMN-IdentityIndexList or PLMN-IdentityList. In this        case, the NR frequency band lists including NR frequency bands        up to a maximum specific constant value (constant TBD) may be        broadcasted.    -   Each NR frequency band may be indicated by FreqBandIndicatorNR,        an absolute radio frequency channel number, or a carrier        frequency.

For example, the broadcasting of the NR frequency band list supporting(NG)EN-DC per PLMN list via the system information, according to anembodiment of the disclosure may be in a form of Table 14 below.

TABLE 14 SystemInformationBlockType1 PLMN-IdentityList PLMN-Identity 1PLMN-Identity 2 PLMN-Identity 3 PLMN-Identity 4SystemInformationBlockType x (x is 1, 2, 5, 24, or 27) NRFreqBandENCD-1, 2, 4 (PLMN- 100, 200, 300 List IdentityIndexList) or (NRFreqENDC-PLMN-Identity 1/2/4 (PLMN- List) IdentityIndexList) 3 (PLMN- 0IdentityIndexList) or PLMN- (NRFreqENDC- Identity 3 List)(PLMN-IdentityIndexList)In the above table, PLMN-Identity 1, PLMN-Identity 2 and PLMN-Identity 4each correspond to the first list of NRFreqBandENCD-List values (100,200, 300), and PLMN-Identity 3 corresponds to the second list ofNRFreqBandENCD-List values (0).

-   -   Because the NR frequency band lists supporting (NG)EN-DC are the        same as 100, 200, 300 for PLMN-Identity 1, PLMN-Identity 2,        PLMN-Identity 4, SysteminformationBlockTypex may include        PLMN-IdentityList including values of PLMN-Identity 1,        PLMN-Identity 2, and PLMN-Identity 4 or PLMN-IdentityIndexList        configured of ‘1’, 2′, and ‘4’. Also, the NR frequency band list        (100, 200, 300) mapped thereto may be broadcasted by being        included in SysteminformationBlockTypex.    -   For PLMN-Identity 3, there may be no NR frequency band        supporting (NG)EN-DC. Here, 0 may be broadcasted or nothing may        be broadcasted. Obviously, SysteminformationBlockTypex may        include PLMN-Identity 3 or may include PLMN index ‘3’ indicating        PLMN-Identity 3.

When the NR frequency band list supporting (NG)EN-DC is the same for allPLMNs, a 1-bit indicator may be introduced. In other words, when the1-bit indicator is set (for example, TRUE), the 1-bit indicator mayindicate that all PLMNs support the same NR frequency band list for(NG)EN-DC when the NR frequency band list supporting (NG)EN-DC isincluded.

In operation 1 h-25, the UE 1 h-01 may receive the system informationincluding the NR frequency band list supporting (NG)EN-DC per PLMN list,as described above. Here, the UE 1 h-01 may receiveSystemInformationBlockType2. In detail, SystemInformationBlockType2 mayinclude an indicator (upperLayerIndication) indicating whether 5Gcapability is provided per PLMN in a same order asSystemInformationBlockType1. An ASN.1 structure is as follows.

-   -   PLMN-InfoList including at least one PLMN-Info may be        broadcasted in SystemInformationBlockType2.    -   Each PLMN-Info may be mapped in a same order of PLMN        Identity/plmn index broadcasted in SystemInformationBlockType1.        In other words, first PLMN-Info may be mapped to plmn index or        plmn-Identity of first PLMN-IdentityInfo broadcasted in        SystemInformationBlockType1.    -   Each PLMN-Info may include upperLayerIndication indicator about        whether a corresponding PLMN provides 5G capability. When        upperLayerIndication is set to TRUE, the corresponding PLMN may        provide 5G capability. Otherwise, the corresponding PLMN may not        provide 5G capability. For reference, upperLayerIndication may        be set to TRUE only when the NR frequency band supporting        (NG)EN-DC is present. This may be represented as Table 15 below.

TABLE 15 PLMN-InfoList-r15 ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-Info-r15 PLMN-Info-r15 ::= SEQUENCE { upperLayerIndication-r15ENUMERATED {true} OPTIONAL -- Need OR } -- ASN1STOP

In operation 1 h-30, the UE 1 h-01 may transmit the upperLayerIndicationto the upper layer when the upperLayerIndication is set to TRUE for thePLMN selected in operation 1 h-20 and at least one NR frequency band issupported in the NR frequency band list for the selected PLMN. In otherwords, the upperLayerIndication may refer to an indicator for indicatingthe upper layer that the UE 1 h-01 has entered or is located in thecoverage area providing 5G capability and the at least one NR frequencyband is supported in the NR frequency band list supported by the cellfor the selected PLMN. Otherwise, the UE 1 h-01 may indicate, to theupper layer, absence of the upperLayerIndication. In other words, the UE1 h-01 may indicate, to the upper layer, the absence of theupperLayerIndication when there is no upperLayerIndication for theselected PLMN, FALSE is set, and/or at least one NR frequency band isnot supported among the NR frequency band list for the selected PLMN.For reference, when the UE 1 h-01 transmits the upperLayerIndication tothe upper layer, the UE 1 h-01 may display a 5G icon on a display of theUE 1 h-01.

In operation 1 h-30, the UE 1 h-01 may transmit, to the upper layer, theupperLayerIndication when information that the upperLayerIndication forthe PLMN registered in operation 1 h-20 or a PLMN belonging to anequivalent PLMN list is set to TRUE and that at least one NR frequencyband is supported in the NR frequency band list for the correspondingPLMN is included. Otherwise, the UE 1 h-01 may indicate, to the upperlayer, absence of the upperLayerIndication.

In operation 1 h-30, the UE 1 h-01 may transmit the upperLayerIndicationto the upper layer when at least one NR frequency band is supported inthe NR frequency band list supporting (NG)EN-DC for the selected PLMN,regardless of the upperLayerIndication being set to TRUE. In otherwords, the upperLayerIndication may denote an indicator for indicatingthe upper layer that the at least one NR frequency band is supported inthe NR frequency band list for (NG)EN-DC supported by the cell for theselected PLMN. Otherwise, the UE 1 h-01 may indicate, to the upperlayer, absence of the upperLayerIndication. For reference, theupperLayerIndication may be used distinguishably from existingupperLayerIndication by introducing a new indicator different from theexisting upperLayerIndication.

FIG. 1I is a diagram for describing a procedure of determining whether aUE 1 i-01 supports a certain NR frequency band, according to anembodiment of the disclosure. Hereinafter, for convenience ofdescription, an example in which the UE 1 i-01 that was operating in anLTE system is located in a coverage area of an NR system is described,but the LTE system and the NR system are only examples, and anembodiment of the disclosure may be applied to another next-generationcommunication system. In detail, FIG. 1I is a diagram for describing aprocedure in which the LTE system determines that the UE 1 i-01 in anRRC idle mode (RRC_IDLE) or RRC inactive mode (RRC_INACTIVE) is locatedin a coverage area providing 5G capability and determines whether aserving cell supports an NR frequency band supporting (NG)EN-DC.

An LTE base station according to an embodiment of the disclosure maysignal whether 5G capability is supported, as system information. Forexample, the LTE base station may signal, to the UE 1 i-01, an NRfrequency band list only for a PLMN supporting (NG)EN-DC, as the systeminformation. Because a specific PLMN may not support (NG)EN-DC, in anembodiment of the disclosure, the NR frequency band list is signaled asthe system information only for the PLMN supporting (NG)EN-DC, and thussignaling overhead may be reduced. As described in the above embodimentof the disclosure, the UE 1 i-01 may determine whether the UE 1 i-01 hasentered or is located in a coverage area supporting 5G capability, basedon an indicator included in the system information. Also, the UE 1 i-01may display a 5G icon by transmitting an indicator indicating the 5Gcapability to an upper layer, based on whether at least one NR frequencyband in the NR frequency band list supporting (NG)EN-DC included in thesystem information is supported.

Referring to FIG. 1I, the UE 1 i-01 may establish an RRC connection witha EUTRA cell 1 i-02 and thus be in an RRC connected mode(RRC_CONNECTED), in operation 1 i-05.

In operation 1 i-10, when there is no data transmission/reception due toa certain reason or for a certain period of time, the EUTRA cell 1 i-02may transmit an RRC connection release message (RRCConnectionRelease) tothe UE 1 i-01. In operation 1 i-10, the RRC connection release messagemay include RRC inactive configuration information (rrc_InactiveConfig).In operation 1 i-15, when the RRC connection release message includesthe RRC inactive configuration information, the UE 1 i-01 may transitionto the RRC inactive mode. When the RRC connection release message doesnot include the RRC inactive configuration information, the UE 1 i-01may transition to the RRC idle mode. In other words, the UE 1 i-01 thatreceived the RRC connection release message may transition to the RRCinactive mode or RRC idle mode depending on whether the RRC inactiveconfiguration information is included in the RRC connection releasemessage.

In operation 1 i-20, the UE 1 i-01 in the RRC idle mode or RRC inactivemode may select a PLMN. The UE 1 i-01 may select the PLMN via a seriesof following processes.

-   -   The UE 1 i-01 may scan all RF channels with respect to E-UTRA        bands depending on capability of the UE 1 i-01.    -   For each carrier, the UE 1 i-01 may find a cell having strongest        signal strength and receive system information from the cell.    -   When at least one PLMN identifier is receivable from the cell        having the strongest signal strength, the UE 1 i-01 may report        an upper layer (for example, NAS) that the at least one PLMN        identifier is a high quality PLMN. Here, when a measured RSRP        value is equal to or greater than −110 dBm, the UE 1 i-01 may        report the upper layer about the high quality PLMN, and when        not, the UE 1 i-01 may report the upper layer together with the        RSRP value.    -   When the UE 1 i-01 supports E-UTRA connected to a 5GC with        respect to a found PLMN, the UE 1 i-01 may also report a CN type        to the upper layer.

In operation 1 i-25, the UE 1 i-01 in the RRC idle mode or RRC inactivemode may perform a cell selection process. The cell selection processmay denote a process for the UE 1 i-01 to camp on a suitable cellassociated to the PLMN selected in operation 1 i-20. The suitable cellmay denote a cell satisfying following conditions.

-   -   When the cell is a part of either the selected PLMN, a        registered PLMN, or a PLMN of an equivalent PLMN list    -   When the cell is not barred according to information provided        from the upper layer    -   When the cell is a part of at least one TA that is not a part of        a list of “forbidden tracking areas for roaming”, which belongs        to the PLMN described above (The cell is part of at least one TA        that is not part of the list of “forbidden tracking areas for        roaming), which belongs to a PLMN that fulfiles the first bullet        above)

In operation 1 i-25, the UE 1 i-01 in the RRC idle mode or RRC inactivemode may receive the system information to perform the cell selectionprocess. In operation 1 i-25, when the UE 1 i-01 receivedSystemInformationBlockType1, a PLMN identity or plmn index correspondingto the PLMN selected in operation 1 i-20 may be included incellAccessRelatedInfoList. In this case, plmn-IdentityList,trackingAreaCode, and cellIdentity for a cell as received in thecorresponding cellAccessRelatedInfoList containing the selected PLMN maybe used. In particular, the plmn-IdentityList may include at least onePLMN-IdentityInfo, and the plmn-IdentityList including at least onePLMN-IdentityInfo for each core type (for example, an evolved packetcore (EPC) and/or 5GC) supported by an LTE cell may be configured. Forexample, PLMN-IdentityInfo of the LTE cell connected to the EPC may beconfigured of plmn-IdentityList up to maxPLMN-r11. For example,maxPLMN-r11 may have a value of 6. Alternatively, PLMN-IdentityInfo ofan LTE cell connected to EPC by defining a new constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. Similarly,PLMN-IdentityInfo of the LTE cell connected to the 5GC may be configuredof plmn-IdentityList up to maxPLMN-r11. For example, maxPLMN-r11 mayhave a value of 6. Alternatively, PLMN-IdentityInfo of the LTE cellconnected to the 5GC based on a newly defined constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. One LTE cell may beconnected only to the EPC, only to the 5GC, or both to the EPC and the5GC.

The plmn-IdentityList may have an ASN.1 structure below.

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the EPC, and each PLMN-IdentityInfo may be        configured of a plmn-Identity value and        cellReservedForOperatorUse. This may be represented as Table 16        below.

TABLE 16 PLMN-IdentityList ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-IdentityInfo PLMN-IdentityInfo ::= SEQUENCE { plmn-IdentityPLMN-Identity, cellReservedForOperatorUse ENUMERATED {reserved,notReserved} }

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the 5GC, and each PLMN-IdentityInfo may        include a plmn index when a same Plmn-Identity as the LTE cell        connected to the EPC is used. For example, when the plmn index        is ‘1’, the plmn index may denote PLMN-Identity included in        first PLMN-IdentityInfo of the LTE cell connected to the EPC.        Also, when the plmn index is ‘2’, the plmn index may denote        PLMN-Identity included in second PLMN-IdentityInfo of the LTE        cell connected to the EPC. In other words, PLMN-IdentityInfo        does not include the same PLMN-Identity value, but includes plmn        index, and thus signaling overhead may be reduced. When        PLMN-Identity different from the LTE cell connected to the EPC        is to be broadcasted to each PLMN-IdentityInfo, the        PLMN-Identity value itself may be included. In other words, the        LTE cell may determine whether to broadcast the PLMN-Identity or        plmn index via a CHOICE structure, and signal a result of the        determination to the UE 1 i-01. Also, PLMN-IdentityInfo may        include cellReservedForOperatorUse for each PLMN. This may be        represented as Table 17 below.

TABLE 17 PLMN-IdentityInfo-r15 ::= SEQUENCE { plmn-Identity-5GC-r15CHOICE{ plmn-Identity-r15 PLMN-Identity, plmn-Index-r15 INTEGER(1..maxPLMN-r11) }, cellReservedForOperatorUse-r15 ENUMERATED {reserved,notReserved}, cellReservedForOperatorUse-CRS-r15 ENUMERATED {reserved,notReserved} }

In operation 1 i-25, the EUTRA cell 1 i-02 according to an embodiment ofthe disclosure may broadcast the NR frequency band list for (NG)EN-DC,as system information, only for the PLMN supporting (NG)EN-DC.

For example, the NR frequency band list for (NG)EN-DC per PLMN list orPLMN may be broadcasted from SystemInformationBlockType1,SystemInformationBlockType2, SystemInformationBlockType5,SystemInformationBlockType24, or new SystemInformationBlockType (forexample, SystemInformationBlockType27). In detail,

-   -   The NR frequency band list for (NG)EN-DC may be included in the        system information only for the PLMN supporting (NG)EN-DC. Here,        the system information may include a PLMN identity and NR        frequency band list corresponding to the PLMN identity. Also,        the system information may include a PLMN index for indicating        the PLMN identity and the NR frequency band list corresponding        to the PLMN index. As described in the above embodiment of the        disclosure, when a plurality of PLMNs support the same NR        frequency band list, the PLMN-IdentityList or        PLMN-IdentityIndexList may be included and a NR frequency band        list corresponding thereto may be included. For example, when        the PLMN index is ‘1’, the PLMN index may indicate plmn-Identity        included in first PLMN-IdentityInfo of plmn-IdentityList        broadcasted via SystemInformationBlockType1.    -   Each NR frequency band may be indicated by FreqBandIndicatorNR,        an absolute radio frequency channel number, or a carrier        frequency.

For example, the broadcasting of the NR frequency band list only forPLMN supporting (NG)EN-DC via the system information, according to anembodiment of the disclosure may be in a form of Table 18 below.

TABLE 18 SystemInformationBlockType1 PLMN-IdentityList PLMN-Identity 1PLMN-Identity 2 PLMN-Identity 3 PLMN-Identity 4SystemInformationBlockType x (x is 1, 2, 5, 24, or 27) NRFreqBandENCD- 4(PLMN- 10, 20, 30 List IdentityIndex) or (NRFreqNR- PLMN-Identity 4List) (PLMN-Identity)In the above table PLMN-Identity 4 corresponds to theNRFreqBandENCD-List values (10, 20, 30).

-   -   For PLMN-Identity 4, an NR frequency band list supporting        (NG)EN-DC may be broadcasted as 10, 20, 30. 10, 20, 30 may        denote FreqBandIndicatorNR. The NR frequency band list may        include a value of PLMN-Identity 4 or a plmn index ‘4’ for        indicating the PLMN-Identity 4.    -   Table 18 may denote that there is no NR frequency band list        supporting (NG)EN-DC in PLMN-Identity 1, PLMN-Identity 2, and        PLMN-Identity 3.

When the NR frequency band list supporting (NG)EN-DC is the same for allPLMNs, a 1-bit indicator may be introduced. In detail, when the 1-bitindicator is set (for example, TRUE), the 1-bit indicator may indicatethat all PLMNs support the same NR frequency band list for (NG)EN-DCwhen the NR frequency band list supporting (NG)EN-DC is included.

In operation 1 i-25, the UE 1 i-01 may receive the system informationincluding the NR frequency band list for the PLMN supporting (NG)EN-DCdescribed above. In operation 1 i-25, the UE 1 i-01 may receiveSystemInformationBlockType2. In detail, SystemInformationBlockType2 mayinclude an indicator (upperLayerIndication) indicating whether 5Gcapability is provided per PLMN in a same order asSystemInformationBlockType1. An ASN.1 structure is as follows.

-   -   PLMN-InfoList including at least one PLMN-Info may be        broadcasted in SystemInformationBlockType2.    -   Each PLMN-Info may be mapped in a same order of PLMN Identity or        plmn index broadcasted in SystemInformationBlockType1. In other        words, first PLMN-Info may be mapped to plmn-Identity of first        PLMN-IdentityInfo broadcasted in SystemInformationBlockType1.    -   Each PLMN-Info may include upperLayerIndication indicator about        whether a corresponding PLMN provides 5G capability. When        upperLayerIndication is set to TRUE, the corresponding PLMN may        provide 5G capability. Otherwise, the corresponding PLMN may not        provide 5G capability. For reference, upperLayerIndication may        be set to TRUE only when the NR frequency band supporting        (NG)EN-DC is present. This may be represented as Table 19 below.

TABLE 19 PLMN-InfoList-r15 ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-Info-r15 PLMN-Info-r15 ::= SEQUENCE { upperLayerIndication-r15ENUMERATED {true} OPTIONAL -- Need OR } -- ASN1STOP

In operation 1 i-30, the UE 1 i-01 may transmit the upperLayerIndicationto the upper layer when the upperLayerIndication is set to TRUE for thePLMN selected in operation 1 i-20 and at least one NR frequency band issupported in the NR frequency band list for (NG)EN-DC for the selectedPLMN. In other words, the upperLayerIndication may refer to an indicatorfor indicating the upper layer that the UE 1 i-01 has entered or islocated in the coverage area providing 5G capability and the at leastone NR frequency band is supported in the NR frequency band list for(NG)EN-DC supported by the cell for the selected PLMN. Otherwise, the UE1 i-01 may indicate the upper layer about absence of theupperLayerIndication. In other words, the UE 1 i-01 may indicate theupper layer about the absence of the upperLayerIndication when there isno upperLayerIndication for the selected PLMN, FALSE is set, and/or atleast one NR frequency band is not supported among the NR frequency bandlist for the selected PLMN. For reference, when the UE 1 i-01 transmitsthe upperLayerIndication to the upper layer, the UE 1 i-01 may display a5G icon on a display of the UE 1 i-01.

In operation 1 i-30, the UE 1 i-01 may transmit, to the upper layer, theupperLayerIndication when information that the upperLayerIndication forthe PLMN registered in operation 1 i-20 or a PLMN belonging to anequivalent PLMN list is set to TRUE and that at least one NR frequencyband is supported in the NR frequency band list for the correspondingPLMN is included. Otherwise, the UE 1 i-01 may indicate, to the upperlayer, absence of the upperLayerIndication.

In operation 1 i-30, the UE 1 i-01 may transmit the upperLayerIndicationto the upper layer when at least one NR frequency band is supported inthe NR frequency band list supporting (NG)EN-DC for the selected PLMN,regardless of the upperLayerIndication being set to TRUE. In otherwords, the upperLayerIndication may denote an indicator for indicatingthe upper layer that the at least one NR frequency band is supported inthe NR frequency band list for (NG)EN-DC supported by the cell for theselected PLMN. Otherwise, the UE 1 i-01 may indicate, to the upperlayer, absence of the upperLayerIndication. For reference, theupperLayerIndication may be used distinguishably from existingupperLayerIndication by introducing a new indicator different from theexisting upperLayerIndication.

FIG. 1J is a diagram for describing a procedure of determining whether aUE 1 j-01 supports a certain NR frequency band, according to anembodiment of the disclosure. Hereinafter, for convenience ofdescription, an example in which the UE 1 j-01 that was operating in anLTE system is located in a coverage area of an NR system is described,but the LTE system and the NR system are only examples, and anembodiment of the disclosure may be applied to another next-generationcommunication system. In detail, FIG. 1J is a diagram for describing aprocedure in which the LTE system determines that the UE 1 j-01 in anRRC idle mode (RRC_IDLE) or RRC inactive mode (RRC_INACTIVE) is locatedin a coverage area providing 5G capability and determines whether aserving cell supports an NR frequency band supporting (NG)EN-DC.

An LTE base station according to an embodiment of the disclosure maysignal whether 5G capability is supported, as system information. Forexample, an LTE base station may signal, to the UE 1 j-01, at least onePLMN per NR frequency band supporting (NG)EN-DC, as the systeminformation. As described in the above embodiment of the disclosure, theUE 1 j-01 determines whether the UE 1 j-01 has entered or is located inthe coverage area supporting 5G capability, based on an indicatorincluded in the system information, and determines whether the NRfrequency band supporting (NG)EN-DC included in the system informationis supported, to thereby display a 5G icon by transmitting the indicatorindicating 5G capability to an upper layer.

Referring to FIG. 1J, the UE 1 j-01 may establish an RRC connection witha EUTRA cell 1 j-02 and thus be in an RRC connected mode(RRC_CONNECTED), in operation 1 j-05. In operation 1 j-10, when there isno data transmission/reception due to a certain reason or for a certainperiod of time, the EUTRA cell 1 j-02 may transmit an RRC connectionrelease message (RRCConnectionRelease) to the UE 1 j-01. In operation 1j-10, the RRC connection release message may include RRC inactiveconfiguration information (rrc_InactiveConfig).

In operation 1 j-15, when an RRC inactive message includes the RRCinactive configuration information, the UE 1 j-01 may transition to theRRC inactive mode. When the RRC inactive message does not include theRRC inactive configuration information, the UE 1 j-01 may transition tothe RRC idle mode. In other words, the UE 1 j-01 that received the RRCconnection release message may transition to the RRC inactive mode orRRC idle mode depending on whether the RRC inactive configurationinformation is included in the RRC connection release message.

In operation 1 j-20, the UE 1 j-01 in the RRC idle mode or RRC inactivemode may select a PLMN. The UE 1 j-01 may select the PLMN via a seriesof following processes.

-   -   The UE 1 j-01 may scan all RF channels with respect to E-UTRA        bands depending on capability of the UE 1 j-01.    -   For each carrier, the UE 1 j-01 may find a cell having strongest        signal strength and receive system information from the cell.    -   When at least one PLMN identifier is receivable from the cell        having the strongest signal strength, the UE 1 j-01 may report        an upper layer (for example, NAS) that the at least one PLMN        identifier is a high quality PLMN. Here, when a measured RSRP        value is equal to or greater than −110 dBm, the UE 1 j-01 may        report the upper layer about the high quality PLMN, and when        not, the UE 1 j-01 may report the upper layer together with the        RSRP value.

When the UE 1 j-01 supports E-UTRA connected to a 5GC with respect to afound PLMN, the UE 1 j-01 may also report a CN type to the upper layer.

In operation 1 j-25, the UE 1 j-01 in the RRC idle mode or RRC inactivemode may perform a cell selection process. The cell selection processmay denote a process for the UE 1 j-01 to camp on a suitable cellassociated to the PLMN selected in operation 1 j-20. The suitable cellmay denote a cell satisfying following conditions.

-   -   When the cell is a part of either the selected PLMN, a        registered PLMN, or a PLMN of an equivalent PLMN list    -   When the cell is not barred according to information provided        from the upper layer    -   When the cell is a part of at least one TA that is not a part of        a list of “forbidden tracking areas for roaming”, which belongs        to the PLMN described above (The cell is part of at least one TA        that is not part of the list of “forbidden tracking areas for        roaming), which belongs to a PLMN that fulfils the first bullet        above)

In operation 1 j-25, the UE 1 j-01 in the RRC idle mode or RRC inactivemode may receive the system information to perform the cell selectionprocess. In operation 1 j-25, when the UE 1 j-01 receivedSystemInformationBlockType1, a PLMN identity or plmn index correspondingto the PLMN selected in operation 1 j-20 may be included incellAccessRelatedInfoList. In this case, plmn-IdentityList,trackingAreaCode, and cellIdentity for a cell as received in thecorresponding cellAccessRelatedInfoList containing the selected PLMN maybe used. In particular, the plmn-IdentityList may include at least onePLMN-IdentityInfo, and the plmn-IdentityList including at least onePLMN-IdentityInfo for each core type (for example, an evolved packetcore (EPC) and/or 5GC) supported by an LTE cell may be configured. Forexample, PLMN-IdentityInfo of the LTE cell connected to the EPC may beconfigured of plmn-IdentityList up to maxPLMN-r11. For example,maxPLMN-r11 may have a value of 6. Alternatively, PLMN-IdentityInfo ofan LTE cell connected to EPC by defining a new constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. Similarly,PLMN-IdentityInfo of the LTE cell connected to the 5GC may be configuredof plmn-IdentityList up to maxPLMN-r11. For example, maxPLMN-r11 mayhave a value of 6. Alternatively, PLMN-IdentityInfo of the LTE cellconnected to the 5GC based on a newly defined constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. One LTE cell may beconnected only to the EPC, only to the 5GC, or both to the EPC and the5GC. The plmn-IdentityList may have an ASN.1 structure below.

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the EPC, and each PLMN-IdentityInfo may be        configured of a plmn-Identity value and        cellReservedForOperatorUse. This may be represented as Table 20        below.

TABLE 20 PLMN-IdentityList ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-IdentityInfo PLMN-IdentityInfo ::= SEQUENCE { plmn-IdentityPLMN-Identity, cellReservedForOperatorUse ENUMERATED {reserved,notReserved} }

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the 5GC, and each PLMN-IdentityInfo may        include a plmn index when a same Plmn-Identity as the LTE cell        connected to the EPC is used. For example, when the plmn index        is ‘1’, the plmn index may denote PLMN-Identity included in        first PLMN-IdentityInfo of the LTE cell connected to the EPC.        Also, when the plmn index is ‘2’, the plmn index may denote        PLMN-Identity included in second PLMN-IdentityInfo of the LTE        cell connected to the EPC. In other words, PLMN-IdentityInfo        does not include the same PLMN-Identity value, but includes plmn        index, and thus signaling overhead may be reduced. When        PLMN-Identity different from the LTE cell connected to the EPC        is to be broadcasted to each PLMN-IdentityInfo, the        PLMN-Identity value itself may be included. In other words, the        LTE cell may determine whether to broadcast the PLMN-Identity or        plmn index via a CHOICE structure, and signal a result of the        determination to the UE 1 j-01. Also, PLMN-IdentityInfo may        include cellReservedForOperatorUse for each PLMN. This may be        represented as Table 21 below.

TABLE 21 PLMN-IdentityInfo-r15 ::= SEQUENCE { plmn-Identity-5GC-r15CHOICE{ plmn-Identity-r15 PLMN-Identity, plmn-Index-r15 INTEGER(1..maxPLMN-r11) }, cellReservedForOperatorUse-r15 ENUMERATED {reserved,notReserved}, cellReservedForOperatorUse-CRS-r15 ENUMERATED {reserved,notReserved} }

In operation 1 j-25, the EUTRA cell 1 j-02 may broadcast at least onePLMN per NR frequency band supporting (NG)EN-DC, as the systeminformation. For example, information about the NR frequency bandsupporting (NG)EN-DC and the at least one PLMN supporting the NRfrequency band may be broadcasted from SystemInformationBlockType1,SystemInformationBlockType2, SystemInformationBlockType5,SystemInformationBlockType24, or new SystemInformationBlockType (forexample, SystemInformationBlockType27). In detail,

-   -   Information about the NR frequency band supporting (NG)EN-DC and        at least one PLMN supporting the NR frequency band may be        included. Here, the information about PLMN may include a value        of PLMN identify itself or a plmn index for indicating the value        of PLMN identity.    -   Each NR frequency band may be indicated by FreqBandIndicatorNR,        an absolute radio frequency channel number, or a carrier        frequency.

For example, the broadcasting of the information about at least one PLMNper NR frequency band supporting (NG)EN-DC via the system information,according to an embodiment of the disclosure may be in a form of Table22 below.

TABLE 22 SystemInformationBlockType x (x is 1, 2, 5, 24, or 27)PLMN-IdentityIn- 1, 2 (PLMN-IdentityIndexList) 10 dexPerNRFreqBandENCD-2, 3 (PLMN-IdentityIndexList) 20 List 3 (PLMN-IdentityIndexList) 300

-   -   An NR frequency band ‘10’ may be supported in PLMN-Identity 1        and PLMN-Identity 2. The system information may include a PLMN        index ‘1’ indicating a PLMN Identity 1 and a PLMN index ‘2’        indicating a PLMN Identity 2, and broadcast the NR frequency        band ‘10’. The system information may include a value of the        PLMN identity itself instead of the PLMN index.    -   To indicate that an NR frequency band ‘20’ is supported in        PLMN-Identity 2 and PLMN-Identity 3, the system information may        include the PLMN index ‘2’ indicating the PLMN Identity 2 and a        PLMN index ‘3’ indicating a PLMN Identity 3, and broadcast the        NR frequency band ‘20’. Also, the system information may include        a value of the PLMN identity itself instead of the PLMN index.    -   To indicate that an NR frequency band ‘300’ is supported in        PLMN-Identity 3, the system information may include the PLMN        index ‘3’ indicating the PLMN Identity 3, and broadcast the NR        frequency band ‘300’. The system information may include a value        of the PLMN identity itself instead of the PLMN index.    -   A PLMN not supporting an NR frequency band may not be signaled.

In addition, information or indicator indicating that a specific NRfrequency band is supported in all PLMNs may be included. For example,an indicator indicating that the specific NR frequency band is supportedin all PLMNs may be set in the system information and the specific NRfrequency band may be included.

In operation 1 j-25, the UE 1 j-01 may receive the system informationincluding the PLMN information per NR frequency band supporting(NG)EN-DC, as described above. In operation 1 j-25, the UE 1 j-01 mayreceive SystemInformationBlockType2. In detail,SystemInformationBlockType2 may include an indicator(upperLayerIndication) indicating whether 5G capability is provided perPLMN in a same order as SystemInformationBlockType1. An ASN.1 structureis as follows.

-   -   PLMN-InfoList including at least one PLMN-Info may be        broadcasted in SystemInformationBlockType2.    -   Each PLMN-Info may be mapped in a same order of PLMN Identity        broadcasted in SystemInformationBlockType1. In other words,        first PLMN-Info may be mapped to plmn-Identity of first        PLMN-IdentityInfo broadcasted in SystemInformationBlockType1.    -   Each PLMN-Info may include upperLayerIndication indicator about        whether a corresponding PLMN provides 5G capability. When        upperLayerIndication is set to TRUE, the corresponding PLMN may        provide 5G capability. Otherwise, the corresponding PLMN may not        provide 5G capability. For reference, upperLayerIndication may        be set to TRUE only when the NR frequency band supporting        (NG)EN-DC is present. This may be represented as Table 23 below.

TABLE 23 PLMN-InfoList-r15 ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-Info-r15 PLMN-Info-r15 ::= SEQUENCE { upperLayerIndication-r15ENUMERATED {true} OPTIONAL -- Need OR } -- ASN1STOP

In operation 1 j-30, the UE 1 j-01 may transmit the upperLayerIndicationto the upper layer when the upperLayerIndication is set to TRUE for thePLMN selected in operation 1 j-20 and at least one NR frequency band for(NG)EN-DC is supported for the selected PLMN. In other words, theupperLayerIndication may refer to an indicator for indicating the upperlayer that the UE 1 j-01 has entered or is located in the coverage areaproviding 5G capability and one NR frequency band for (NG)EN-DCsupported by at least a cell for the selected PLMN is supported.Otherwise, the UE 1 j-01 may indicate, to the upper layer, absence ofthe upperLayerIndication. In other words, the UE 1 j-01 may indicate, tothe upper layer, the absence of the upperLayerIndication when there isno upperLayerIndication for the selected PLMN, FALSE is set, and/or atleast one NR frequency band for (NG)EN-DC is not supported for theselected PLMN. For reference, when the UE 1 j-01 transmits theupperLayerIndication to the upper layer, the UE 1 j-01 may display a 5Gicon on a display of the UE 1 j-01.

In operation 1 j-30, the UE 1 j-01 may transmit, to the upper layer, theupperLayerIndication when information that the upperLayerIndication forthe PLMN registered in operation 1 j-20 or a PLMN belonging to anequivalent PLMN list is set to TRUE and that at least one NR frequencyband for (NG)EN-DC is supported for the corresponding PLMN is included.Otherwise, the UE 1 j-01 may indicate, to the upper layer, absence ofthe upperLayerIndication.

In operation 1 j-30, the UE 1 j-01 may transmit the upperLayerIndicationto the upper layer when at least one NR frequency band supporting(NG)EN-DC is supported for the selected PLMN, regardless of theupperLayerIndication being set to TRUE. In other words, theupperLayerIndication may denote an indicator for indicating the upperlayer that the at least one NR frequency band for (NG)EN-DC supported bythe cell for the selected PLMN is supported. Otherwise, the UE 1 j-01may indicate, to the upper layer, absence of the upperLayerIndication.For reference, the upperLayerIndication may be used distinguishably fromexisting upperLayerIndication by introducing a new indicator differentfrom the existing upperLayerIndication.

FIG. 1K is a diagram for describing a procedure of determining whether aUE 1 k-01 supports a certain frequency range, according to an embodimentof the disclosure. Hereinafter, for convenience of description, anexample in which the UE 1 k-01 that was operating in an LTE system islocated in a coverage area of an NR system is described, but the LTEsystem and the NR system are only examples, and an embodiment of thedisclosure may be applied to another next-generation communicationsystem. In detail, FIG. 1K is a diagram for describing a procedure ofdetermining that the UE 1 k-01 in an RRC idle mode (RRC_IDLE) or RRCinactive mode (RRC_INACTIVE) is located in a coverage area providing 5Gcapability and determining whether a serving cell supports an NRfrequency range supporting (NG)EN-DC.

A EUTRA cell 1 k-02 according to an embodiment of the disclosure maysignal whether 5G capability is supported, as system information. Forexample, the EUTRA cell 1 k-02 may signal, to the UE 1 k-01, an NRfrequency range supporting (NG)EN-DC for per PLMN, as the systeminformation. As described in the above embodiment of the disclosure, theUE 1 k-01 may determine whether the UE 1 k-01 has entered or is locatedin the coverage area supporting 5G capability, based on an indicatorincluded in the system information, determine whether the broadcasted NRfrequency range is supported, determine whether the NR frequency rangesupporting (NG)EN-DC included in the system information is supported,and display a 5G icon by transmitting an indicator indicating the 5Gcapability to an upper layer.

Referring to FIG. 1K, the UE 1 k-01 may establish an RRC connection withthe EUTRA cell 1 k-02 and thus be in an RRC connected mode(RRC_CONNECTED), in operation 1 k-05.

In operation 1 k-10, when there is no data transmission/reception due toa certain reason or for a certain period of time, the EUTRA cell 1 k-02may transmit an RRC connection release message (RRCConnectionRelease) tothe UE 1 k-01. In operation 1 k-10, the RRC connection release messagemay include RRC inactive configuration information (rrc_InactiveConfig).

In operation 1 k-15, when the RRC connection release message includesthe RRC inactive configuration information, the UE 1 k-01 may transitionto the RRC inactive mode. When the RRC connection release message doesnot include the RRC inactive configuration information, the UE 1 k-01may transition to the RRC idle mode, in operation 1 k-15. In otherwords, the UE 1 k-01 that received the RRC connection release messagemay transition to the RRC inactive mode or RRC idle mode depending onwhether the RRC inactive configuration information is included in theRRC connection release message.

In operation 1 k-20, the UE 1 k-01 in the RRC idle mode or RRC inactivemode may select a PLMN. The UE 1 k-01 may select the PLMN via a seriesof following processes.

-   -   The UE 1 k-01 may scan all RF channels with respect to E-UTRA        bands depending on capability of the UE 1 k-01.    -   For each carrier, the UE 1 k-01 may find a cell having strongest        signal strength and receive system information from the cell.    -   When at least one PLMN identifier is receivable from the cell        having the strongest signal strength, the UE 1 k-01 may report        an upper layer (for example, NAS) that the at least one PLMN        identifier is a high quality PLMN. Here, when a measured RSRP        value is equal to or greater than −110 dBm, the UE 1 k-01 may        report the upper layer about the high quality PLMN, and when        not, the UE 1 k-01 may report the upper layer together with the        RSRP value.    -   When the UE 1 k-01 supports E-UTRA connected to a 5GC with        respect to a found PLMN, the UE 1 k-01 may also report a CN type        to the upper layer.

In operation 1 k-25, the UE 1 k-01 in the RRC idle mode or RRC inactivemode may perform a cell selection process. The cell selection processmay denote a process for the UE 1 k-01 to camp on a suitable cellassociated to the PLMN selected in operation 1 k-20. The suitable cellmay denote a cell satisfying following conditions.

-   -   When the cell is a part of either the selected PLMN, a        registered PLMN, or a PLMN of an equivalent PLMN list    -   When the cell is not barred according to information provided        from the upper layer    -   When the cell is a part of at least one TA that is not a part of        a list of “forbidden tracking areas for roaming”, which belongs        to the PLMN described above (The cell is part of at least one TA        that is not part of the list of “forbidden tracking areas for        roaming), which belongs to a PLMN that fulfiles the first bullet        above)

In operation 1 k-25, the UE 1 k-01 in the RRC idle mode or RRC inactivemode may receive the system information to perform the cell selectionprocess.

In operation 1 k-25, when the UE 1 k-01 receivedSystemInformationBlockType1, a PLMN identity or plmn index correspondingto the PLMN selected in operation 1 k-20 may be included incellAccessRelatedInfoList. In this case, plmn-IdentityList,trackingAreaCode, and cellIdentity for a cell as received in thecorresponding cellAccessRelatedInfoList containing the selected PLMN maybe used. In particular, the plmn-IdentityList may include at least onePLMN-IdentityInfo, and the plmn-IdentityList including at least onePLMN-IdentityInfo for each core type (for example, an evolved packetcore (EPC) and/or 5GC) supported by an LTE cell may be configured. Forexample, PLMN-IdentityInfo of the LTE cell connected to the EPC may beconfigured of plmn-IdentityList up to maxPLMN-r11. For example,maxPLMN-r11 may have a value of 6. Alternatively, PLMN-IdentityInfo ofan LTE cell connected to EPC based on a newly defined constant value maybe configured of plmn-IdentityList up to maxPLMN-r16. Similarly,PLMN-IdentityInfo of the LTE cell connected to the 5GC may be configuredof plmn-IdentityList up to maxPLMN-r11. For example, maxPLMN-r11 mayhave a value of 6. Alternatively, PLMN-IdentityInfo of the LTE cellconnected to the 5GC based on a newly defined constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. One LTE cell may beconnected only to the EPC, only to the 5GC, or both to the EPC and the5GC. The plmn-IdentityList may have an ASN.1 structure below.

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the EPC, and each PLMN-IdentityInfo may be        configured of a plmn-Identity value and        cellReservedForOperatorUse. This may be represented as Table 24        below.

TABLE 24 PLMN-IdentityList ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-IdentityInfo PLMN-IdentityInfo ::= SEQUENCE { plmn-IdentityPLMN-Identity, cellReservedForOperatorUse ENUMERATED {reserved,notReserved} }

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the 5GC, and each PLMN-IdentityInfo may        include a plmn index when a same Plmn-Identity as the LTE cell        connected to the EPC is used. For example, when the plmn index        is ‘1’, the plmn index may denote PLMN-Identity included in        first PLMN-IdentityInfo of the LTE cell connected to the EPC.        Also, when the plmn index is ‘2’, the plmn index may denote        PLMN-Identity included in second PLMN-IdentityInfo of the LTE        cell connected to the EPC. In other words, PLMN-IdentityInfo        does not include the same PLMN-Identity value, but includes plmn        index, and thus signaling overhead may be reduced. When        PLMN-Identity different from the LTE cell connected to the EPC        is to be broadcasted to each PLMN-IdentityInfo, the        PLMN-Identity value itself may be included. In other words, the        LTE cell may determine whether to broadcast the PLMN-Identity or        plmn index via a CHOICE structure, and signal a result of the        determination to the UE 1 k-01. Also, PLMN-IdentityInfo may        include cellReservedForOperatorUse for each PLMN. This may be        represented as Table 25 below.

TABLE 25 PLMN-IdentityInfo-r15 ::= SEQUENCE { plmn-Identity-5GC-r15CHOICE{ plmn-Identity-r15 PLMN-Identity, plmn-Index-r15 INTEGER(1..maxPLMN-r11) }, cellReservedForOperatorUse-r15 ENUMERATED {reserved,notReserved}, cellReservedForOperatorUse-CRS-r15 ENUMERATED {reserved,notReserved} }

In operation 1 k-25, the EUTRA cell 1 k-02 may broadcast the NRfrequency range supporting (NG)EN-DC per PLMN, as the systeminformation. For example, NR frequency range information supporting(NG)EN-DC per PLMN may be broadcasted from SystemInformationBlockType1,SystemInformationBlockType2, SystemInformationBlockType5,SystemInformationBlockType24, or new SystemInformationBlockType (forexample, SystemInformationBlockType27). For example,

-   -   The NR frequency range information supporting (NG)EN-DC per PLMN        may be included. Here, information about PLMN may include a        value of PLMN identify itself or a plmn index for indicating the        value of PLMN identity. Alternatively, the NR frequency range        information may be included in a same order as the PLMN included        in SystemInformationBlockType1. Here, when a specific PLMN does        not support an NR frequency range, information indicating that        the NR frequency range is not supported may be additionally        signaled. For example, it may be indicated that the NR frequency        range is not supported by broadcasting an indicator indicating        that the NR frequency range is not supported or by not        broadcasting information about a frequency range (FR).    -   FR1, FR2, or both FR1 and FR2 may be included for the NR        frequency range supporting (NG)EN-DC per PLMN.

For example, the broadcasting of the NR frequency range informationsupporting (NG)EN-DC per PLMN, as the system information, may be in aform of Table 26 below.

TABLE 26 SystemInformationBlockType1 PLMN-IdentityList PLMN-Identity 1PLMN-Identity 2 PLMN-Identity 3 SystemInformationBlockType x (x is 1, 2,5, 24, or 27) NRFreqBandENCD-List FR1, FR2 FR1 absentIn the above table, PLMN-Identity 1 corresponds to the first list ofNRFreqBandENCD-List values (FR1, FR2), PLMN-Identity 2 corresponds tothe second list of NRFreqBandENCD-List values (FR1), and PLMN-Identity 3corresponds to the third list of NRFreqBandENCD-List values (absent).

-   -   PLMN-Identity 1 may indicate that FR1 and FR2 support (NG)EN-DC        by including FR1 and FR2.    -   PLMN-Identity 2 may indicate that FR1 supports (NG)EN-DC by        including FR1.    -   PLMN-Identity 3 may indicate that (NG)EN-DC is not supported        because no value is included.

Unlike Table 26, FR information may be signaled only for the PLMNsupporting (NG)EN-DC.

In operation 1 k-25, the UE 1 k-01 may receive the system informationincluding the NR frequency range information for the PLMN supporting(NG)EN-DC described above.

In operation 1 k-25, the UE 1 k-01 may receiveSystemInformationBlockType2. In detail, SystemInformationBlockType2 mayinclude an indicator (upperLayerIndication) indicating whether 5Gcapability is provided per PLMN in a same order asSystemInformationBlockType1. An ASN.1 structure is as follows.

-   -   PLMN-InfoList including at least one PLMN-Info may be        broadcasted in SystemInformationBlockType2.    -   Each PLMN-Info may be mapped in a same order of PLMN Identity        broadcasted in SystemInformationBlockType1. In other words,        first PLMN-Info may be mapped to plmn-Identity of first        PLMN-IdentityInfo broadcasted in SystemInformationBlockType1.    -   Each PLMN-Info may include upperLayerIndication indicator about        whether 5G capability is provided. When upperLayerIndication is        set to TRUE, the corresponding PLMN may provide 5G capability.        Otherwise, the corresponding PLMN may not provide 5G capability.        For reference, upperLayerIndication may be set to TRUE only when        the NR frequency range supporting (NG)EN-DC is present. This may        be represented as Table 27 below.

TABLE 27 PLMN-InfoList-r15 ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-Info-r15 PLMN-Info-r15 ::= SEQUENCE { upperLayerIndication-r15ENUMERATED {true} OPTIONAL -- Need OR } -- ASN1STOP

In operation 1 k-30, the UE 1 k-01 may transmit the upperLayerIndicationto the upper layer when the upperLayerIndication is set to TRUE for thePLMN selected in operation 1 k-20 and the NR frequency range issupported for the selected PLMN. In other words, theupperLayerIndication may refer to an indicator for indicating the upperlayer that the UE 1 k-01 has entered or is located in the coverage areaproviding 5G capability and at least one NR frequency range is supportedin an NR frequency range list supported by the cell for the selectedPLMN. Otherwise, the UE 1 k-01 may indicate, to the upper layer, absenceof the upperLayerIndication. In other words, the UE 1 k-01 may indicate,to the upper layer, the absence of the upperLayerIndication when thereis no upperLayerIndication for the selected PLMN, FALSE is set, and/orat least one NR frequency range is not supported among the NR frequencyrange list for the selected PLMN. For reference, when the UE 1 k-01transmits the upperLayerIndication to the upper layer, the UE 1 k-01 maydisplay a 5G icon on a display of the UE 1 k-01.

In operation 1 k-30, the UE 1 k-01 may transmit, to the upper layer, theupperLayerIndication when the upperLayerIndication for the PLMNregistered in operation 1 k-20 or a PLMN belonging to an equivalent PLMNlist is set to TRUE and that at least one NR frequency range issupported in the NR frequency range list for the corresponding PLMN.Otherwise, the UE 1 k-01 may indicate, to the upper layer, absence ofthe upperLayerIndication.

In operation 1 k-30, the UE 1 k-01 may transmit the upperLayerIndicationto the upper layer when at least one NR frequency range supporting(NG)EN-DC is supported for the selected PLMN, regardless of theupperLayerIndication being set to TRUE. In other words, theupperLayerIndication may denote an indicator for indicating the upperlayer that the at least one NR frequency range for (NG)EN-DC supportedby the cell for the selected PLMN is supported. Otherwise, the UE 1 k-01may indicate, to the upper layer, absence of the upperLayerIndication.For reference, the upperLayerIndication may be used distinguishably fromexisting upperLayerIndication by introducing a new indicator differentfrom the existing upperLayerIndication.

FIG. 1L is a diagram for describing a procedure of determining whether aUE 1 l-01 supports a certain frequency band, according to an embodimentof the disclosure. Hereinafter, for convenience of description, anexample in which the UE 1 l-01 that was operating in an LTE system islocated in a coverage area of an NR system is described, but the LTEsystem and the NR system are only examples, and an embodiment of thedisclosure may be applied to another next-generation communicationsystem. In detail, FIG. 1L is a diagram for describing a procedure inwhich the LTE system determines that the UE 1 l-01 in an RRC idle mode(RRC_IDLE) or RRC inactive mode (RRC_INACTIVE) is located in a coveragearea providing 5G capability and determines whether a serving cellsupports an NR frequency band supporting (NG)EN-DC.

An LTE base station according to an embodiment of the disclosure maysignal whether 5G capability is supported, as system information. Forexample, the LTE base station may signal, to the UE 1 l-01, a NRfrequency band list supporting (NG)EN-DC for each PLMN, as the systeminformation. According to an embodiment of the disclosure, because allNR frequency bands may be supported for a specific PLMN, 1 bit may beintroduced to indicate that all NR frequency bands are supported withoutincluding an NR frequency band list or it may be indicated that all NRfrequency bands are supported by not including the NR frequency bandlist. In addition, 1 bit may be introduced per NR frequency range toindicate whether all NR frequency band lists are supported for FR1 andwhether all NR frequency band lists are supported for FR2. In this case,signaling overhead may be reduced because all NR frequency band listsare not included in the system information for the specific PLMN. Asdescribed in the above embodiment of the disclosure, the UE 1 l-01determines whether the UE 1 l-01 has entered or is located in thecoverage area supporting 5G capability, based on an indicator includedin the system information, and determines whether at least one NRfrequency band among the signaled NR frequency band list is supported,to thereby transmit the indicator indicating 5G capability to an upperlayer and display a 5G icon.

Referring to FIG. 1L, the UE 1 l-01 may establish an RRC connection witha EUTRA cell 1 l-02 and thus be in an RRC connected mode(RRC_CONNECTED), in operation 1 l-05.

In operation 1 l-10, when there is no data transmission/reception due toa certain reason or for a certain period of time, the EUTRA cell 1 l-02may transmit an RRC connection release message (RRCConnectionRelease) tothe UE 1 l-01. In operation 1 l-10, the RRC connection release messagemay include RRC inactive configuration information (rrc_InactiveConfig).

In operation 1 l-15, when the RRC inactive configuration information isincluded, the UE 1 l-01 may transition to the RRC inactive mode. Whenthe RRC inactive configuration information is not included, the UE 1l-01 may transition to the RRC idle mode. In other words, the UE 1 l-01that received the RRC connection release message may transition to theRRC inactive mode or RRC idle mode depending on whether the RRC inactiveconfiguration information is included.

In operation 1 l-20, the UE 1 l-01 in the RRC idle mode or RRC inactivemode may select a PLMN. The UE 1 l-01 may select the PLMN via a seriesof following processes.

-   -   The UE 1 l-01 may scan all RF channels with respect to E-UTRA        bands depending on capability of the UE 1 l-01.    -   For each carrier, the UE 1 l-01 may find a cell having strongest        signal strength and receive system information from the cell.    -   When at least one PLMN identifier is receivable from the cell        having the strongest signal strength, the UE 1 l-01 may report        an upper layer (for example, NAS) that the at least one PLMN        identifier is a high quality PLMN. Here, when a measured RSRP        value is equal to or greater than −110 dBm, the UE 1 l-01 may        report the upper layer about the high quality PLMN, and when        not, the UE 1 l-01 may report the upper layer together with the        RSRP value.    -   When the UE 1 l-01 supports E-UTRA connected to a 5GC with        respect to a found PLMN, the UE 1 l-01 may also report a CN type        to the upper layer.

In operation 1 l-25, the UE 1 l-01 in the RRC idle mode or RRC inactivemode may perform a cell selection process. The cell selection processmay denote a process for the UE 1 l-01 to camp on a suitable cellassociated to the PLMN selected in operation 1 l-20. The suitable cellmay denote a cell satisfying following conditions.

-   -   When the cell is a part of either the selected PLMN, a        registered PLMN, or a PLMN of an equivalent PLMN list    -   When the cell is not barred according to information provided        from the upper layer    -   When the cell is a part of at least one TA that is not a part of        a list of “forbidden tracking areas for roaming”, which belongs        to the PLMN described above (The cell is part of at least one TA        that is not part of the list of “forbidden tracking areas for        roaming), which belongs to a PLMN that fulfiles the first bullet        above)

In operation 1 l-25, the UE 1 l-01 in the RRC idle mode or RRC inactivemode may receive the system information to perform the cell selectionprocess.

In operation 1 l-25, when the UE 1 l-01 receivedSystemInformationBlockType1, a PLMN identity or plmn index correspondingto the PLMN selected in operation 1 l-20 may be included incellAccessRelatedInfoList. In this case, plmn-IdentityList,trackingAreaCode, and cellIdentity for a cell as received in thecorresponding cellAccessRelatedInfoList containing the selected PLMN maybe used. In particular, the plmn-IdentityList may include at least onePLMN-IdentityInfo, and the plmn-IdentityList including at least onePLMN-IdentityInfo for each core type (for example, an evolved packetcore (EPC) and/or 5GC) supported by an LTE cell may be configured. Forexample, PLMN-IdentityInfo of the LTE cell connected to the EPC may beconfigured of plmn-IdentityList up to maxPLMN-r11. For example,maxPLMN-r11 may have a value of 6. Alternatively, PLMN-IdentityInfo ofan LTE cell connected to EPC by defining a new constant value may beconfigured of plmn-IdentityList up to maxPLMN-r16. Similarly,PLMN-IdentityInfo of the LTE cell connected to the 5GC may be configuredof plmn-IdentityList up to maxPLMN-r11. For example, maxPLMN-r11 mayhave a value of 6. Alternatively, PLMN-IdentityInfo of an LTE cellconnected to 5GC by defining a new constant value may be configured ofplmn-IdentityList up to maxPLMN-r16. One LTE cell may be connected onlyto the EPC, only to the 5GC, or both to the EPC and the 5GC. Theplmn-IdentityList may have an ASN.1 structure below.

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the EPC, and each PLMN-IdentityInfo may be        configured of a plmn-Identity value and        cellReservedForOperatorUse. This may be represented as Table 28        below.

TABLE 28 PLMN-IdentityList ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-IdentityInfo PLMN-IdentityInfo ::= SEQUENCE { plmn-IdentityPLMN-Identity, cellReservedForOperatorUse ENUMERATED {reserved,notReserved} }

-   -   At least one PLMN-IdentityInfo may be configured for the LTE        cell connected to the 5GC, and each PLMN-IdentityInfo may        include a plmn index when a same Plmn-Identity as the LTE cell        connected to the EPC is used. For example, when the plmn index        is ‘1’, the plmn index may denote PLMN-Identity included in        first PLMN-IdentityInfo of the LTE cell connected to the EPC,        and when the plmn index is ‘2’, the plmn index may denote        PLMN-Identity included in second PLMN-IdentityInfo of the LTE        cell connected to the EPC. By including the plmn index instead        of a same value of PLMN-Identity, signaling overhead may be        reduced. When PLMN-Identity different from the LTE cell        connected to the EPC is to be broadcasted to each        PLMN-IdentityInfo, the PLMN-Identity value itself may be        included. In other words, the LTE cell may determine whether to        broadcast the PLMN-Identity or plmn index via a CHOICE        structure, and signal a result of the determination to the UE 1        l-01. Also, cellReservedForOperatorUse may be included for each        PLMN.

In operation 1 l-25, the EUTRA cell 1 l-02 according to an embodiment ofthe disclosure may broadcast the NR frequency band list supporting(NG)EN-DC per PLMN, as the system information. For example, the NRfrequency band list supporting (NG)EN-DC per PLMN may be broadcastedfrom SystemInformationBlockType1, SystemInformationBlockType2,SystemInformationBlockType5, SystemInformationBlockType24, or newSystemInformationBlockType (for example, SystemInformationBlockType27).According to an embodiment of the disclosure, when all NR frequency bandlists supporting (NG)EN-DC are supported for the specific PLMN, 1 bitmay be introduced to indicate the same. Alternatively, 1 bit per FR maybe introduced for the specific PLMN to indicate whether all NR frequencyband lists supporting (NG)EN-DC per FR are supported. Also, it may beindicated that all NR frequency band lists are supported by notincluding the NR frequency band list, when all NR frequency band listssupporting (NG)EN-DC are supported for the specific PLMN, withoutintroducing 1 bit. Alternatively, it may be indicated that all NRfrequency band lists per FR are supported by not including the NRfrequency band list, when all NR frequency band lists supporting(NG)EN-DC per FR are supported for the specific PLMN.

For example,

-   -   1 bit may be included to indicate that all NR frequency band        lists supporting (NG)EN-DC are supported for the specific PLMN.        Alternatively, it may be indicated that all NR frequency band        lists are supported by not including the NR frequency band list.    -   1 bit may be included to indicate that all NR frequency band        lists supporting (NG)EN-DC are supported per FR for the specific        PLMN. Alternatively, it may be indicated that all NR frequency        band lists are supported by not including the NR frequency band        list per FR.    -   According to the embodiments of the disclosure described above,        the NR frequency band list may be included for the PLMN        supporting (NG)EN-DC, or the NR frequency band list may be        included for the PLMN in a same order as PLMN included in        SystemInformationBlockType1. Alternatively, PLMN information and        NR frequency band supporting (NG)EN-DC per NR frequency band may        be included.    -   Each NR frequency band may be indicated by FreqBandIndicatorNR,        an absolute radio frequency channel number, or a carrier        frequency.

In operation 1 l-25, the UE 1 l-01 may receive the system informationincluding the NR frequency band list supporting (NG)EN-DC per PLMNdescribed above. In operation 1 i-25, SystemInformationBlockType2 may bereceived. In detail, SystemInformationBlockType2 may include anindicator (upperLayerIndication) indicating whether 5G capability isprovided per PLMN in a same order as SystemInformationBlockType1. AnASN.1 structure is as follows.

-   -   PLMN-InfoList including at least one PLMN-Info may be        broadcasted in SystemInformationBlockType2.    -   Each PLMN-Info may be mapped in a same order of PLMN Identity        broadcasted in SystemInformationBlockType1. In other words,        first PLMN-Info may be mapped to plmn-Identity of first        PLMN-IdentityInfo broadcasted in SystemInformationBlockType1.    -   Each PLMN-Info may include upperLayerIndication indicator about        whether 5G capability is provided. When upperLayerIndication is        set to TRUE, the corresponding PLMN may provide 5G capability.        Otherwise, the corresponding PLMN may not provide 5G capability.        For reference, upperLayerIndication may be set to TRUE only when        the NR frequency range supporting (NG)EN-DC is present. This may        be represented as Table 29 below.

TABLE 29 PLMN-InfoList-r15 ::= SEQUENCE (SIZE (1..maxPLMN-r11)) OFPLMN-Info-r15 PLMN-Info-r15 ::= SEQUENCE { upperLayerIndication-r15ENUMERATED (true) OPTIONAL -- Need OR } -- ASN1STOP

In operation 1 l-30, the UE 1 l-01 may transmit the upperLayerIndicationto the upper layer when the upperLayerIndication is set to TRUE for thePLMN selected in operation 1 l-20 and at least one NR frequency band issupported in the NR frequency band list for the selected PLMN. TheupperLayerIndication may refer to an indicator for indicating the upperlayer that the UE 1 l-01 has entered the coverage area providing 5Gcapability and the at least one NR frequency band is supported in the NRfrequency band list supported by the cell for the selected PLMN.Otherwise, the UE 1 l-01 may indicate, to the upper layer, absence ofthe upperLayerIndication. In other words, the UE 1 l-01 may indicate, tothe upper layer, the absence of the upperLayerIndication when there isno upperLayerIndication for the selected PLMN, FALSE is set, and/or atleast one NR frequency band is not supported among the NR frequency bandlist for the selected PLMN. For reference, when the UE 1 l-01 transmitsthe upperLayerIndication to the upper layer, the UE 1 l-01 may display a5G icon on a display of the UE 1 l-01.

Alternatively, in operation 1 l-30, the UE 1 l-01 may transmit, to theupper layer, the upperLayerIndication when the upperLayerIndication forthe PLMN registered in operation 1 l-20 or a PLMN belonging to anequivalent PLMN list is set to TRUE and that at least one NR frequencyband is supported in the NR frequency band list for the correspondingPLMN. Otherwise, the UE 1 l-01 may indicate, to the upper layer, absenceof the upperLayerIndication.

Alternatively, in operation 1 l-30, the UE 1 l-01 may transmit theupperLayerIndication to the upper layer when at least one NR frequencyband supporting (NG)EN-DC is supported for the selected PLMN, regardlessof the upperLayerIndication being set to TRUE. In other words, theupperLayerIndication may denote an indicator for indicating the upperlayer that the at least one NR frequency band for (NG)EN-DC supported bythe cell for the selected PLMN is supported. Otherwise, the UE 1 l-01may indicate, to the upper layer, absence of the upperLayerIndication.For reference, the upperLayerIndication may be used distinguishably fromexisting upperLayerIndication by introducing a new indicator differentfrom the existing upperLayerIndication.

FIG. 1M is a diagram for describing a procedure of determining whether aUE 1 m-01 supports a certain frequency band or frequency range,according to an embodiment of the disclosure. Hereinafter, forconvenience of description, an example in which the UE 1 m-01 that wasoperating in an LTE system is located in a coverage area of an NR systemis described, but the LTE system and the NR system are only examples,and an embodiment of the disclosure may be applied to anothernext-generation communication system. FIG. 1M is a diagram fordescribing a procedure of determining that the UE 1 m-01 in an RRC idlemode (RRC_IDLE) or RRC inactive mode (RRC_INACTIVE) is located in acoverage area providing 5G capability and determining whether an NRfrequency band or NR frequency range supporting (NG)EN-DC is supported.

A base station according to an embodiment of the disclosure may addsystem information including whether 5G capability is supported indedicated signaling and provide the same to the UE 1 m-01. For example,the dedicated signaling may denote an RRCConnectionReconfigurationmessage. The system information included in the dedicated signaling mayfollow the above-described embodiment of the disclosure. The UE 1 m-01in an RRC connected mode may determine that the UE 1 m-01 has enteredthe coverage area supporting the 5G capability, based on the systeminformation added to the dedicated signaling and determine whether theNR frequency band or NR frequency range is supported, to thereby displaya 5G icon by transmitting an indicator indicating the 5G capability toan upper layer.

Referring to FIG. 1M, the UE 1 m-01 may establish an RRC connection witha EUTRA cell 1 m-02 and thus be in the RRC connected mode(RRC_CONNECTED), in operation 1 m-05.

In operation 1 m-10, the UE 1 m-01 in the RRC connected mode maytransmit, to the EUTRA cell 1 m-02, a UE capability information message.The UE capability information message may include at least one of anindicator about whether EN-DC is supported, an indicator about whether(NG)EN-DC is supported, or an NR frequency band list supported in(NG)EN-DC (supportedBandListEN-DC). For reference, thesupportedBandListEN-DC is a list commonly applied to EN-DC and(NG)EN-DC. This is because the supportedBandListEN-DC is informationabout RF and is irrelevant from a core.

In operation 1 m-15, the EUTRA cell 1 m-02 may establish (NG)EN-DC bytransmitting an RRC connection reconfiguration message(RRCConnectionReconfiguration) to the UE 1 m-01 in the RRC connectedmode. The RRC connection reconfiguration message may include at leastone of nr-SecondaryCellGroupConfig, nr-RadioBearerConfig1, ornr-RadioBearerConfig2.

In operation 1 m-20, the UE 1 m-01 in the RRC connected mode may applyinformation included in the received RRC connection reconfigurationmessage and transmit an RRC connection reconfiguration complete message(RRCConnectionReconfigurationComplete) to the EUTRA cell 1 m-02.

In operation 1 m-25, the UE 1 m-01 in the RRC connected mode mayreceive, from the EUTRA cell 1 m-02, an RRC connection reconfigurationmessage including a mobilityControlInfo element.

Based on the embodiment of the disclosure described above, the RRCconnection reconfiguration message may be transmitted to the UE 1 m-01via RRC connection, by including system information (for example,SystemInformationBlockType 1, 2, 5, 24, or new) in which NR frequencyband (list) or NR frequency range information supporting (NG)EN-DC isincluded. When the UE 1 m-01 supports EN-DC and/or EUTRA-5GC, the EUTRAcell 1 m-02 may transmit the system information to the UE 1 m-01 byadding the system information to the RRC connection reconfigurationmessage. Alternatively, the EUTRA cell 1 m-02 may transmit, to the UE 1m-01 supporting (NG)EN-DC, the RRC connection reconfiguration message(RRCConnectionReconfiguration) including SystemInformationBlockType24.

In operation 1 m-30, the UE 1 m-01 in the RRC connected mode mayindicate presence of upperLayerIndication to an upper layer when theupperLayerIndication is set to TRUE for a registered PLMN, a selectedPLMN, or a PLMN belonging to an equivalent PLMN list inSystemInformationBlockType2 broadcasted from a current cell (forexample, a cell that performed handover) and when the UE 1 m-01 supportsat least one NR frequency band for (NG)EN-DC for the corresponding PLMN.Information about the NR frequency band for (NG)EN-DC may be included inthe RRC connection reconfiguration message received in operation 1 m-25.When the upperLayerIndication is not set to TRUE (for example, is set toabsent or FALSE) for the registered PLMN, the selected PLMN, or the PLMNbelonging to the equivalent PLMN list in SystemInformationBlockType2broadcasted from the cell or when the upperLayerIndication is set toTRUE but the at least one NR frequency band for (NG)EN-DC is notsupported, absence of the upperLayerIndication may be indicated to theupper layer.

In operation 1 m-30, the UE 1 m-01 in the RRC connected mode mayindicate the presence of the upperLayerIndication to the upper layerwhen the at least one NR frequency band for (NG)EN-DC included in theRRC connection reconfiguration message received in operation 1 m-25 issupported. When the at least one NR frequency band for (NG)EN-DC is notsupported, the UE 1 m-01 may indicate the absence ofupperLayerIndication to the upper layer.

Alternatively, in operation 1 m-30, the UE 1 m-01 in the RRC connectedmode may indicate the absence of upperLayerIndication to the upper layerwhen the RRC connection reconfiguration message received in operation 1m-25 does not include the system information (for example,SystemInformationBlockType 1, 2, 5, 24, or new) including the NRfrequency band (list) or NR frequency range supporting (NG)EN-DC.

In operation 1 m-25, the EUTRA cell 1 m-02 may transmit, to the UE 1m-01, the system information included in the RRC connectionreconfiguration message by configuring the system information in a formof delta signaling. Because the UE 1 m-01 received information about theNR frequency band list for (NG)EN-DC when entering an RRC connectedstate, the delta signaling may indicate including only information abouta change in the cell that performed handover. For example, the EUTRAcell 1 m-02 may provide information about only a PLMN not suitable tothe UE 1 m-01. In other words, the system information including onlyinformation about a PLMN not supporting the NR frequency band (list) orNR frequency range for (NG)EN-DC may be transmitted to the UE 1 m-01 byincluding the system information in the RRC connection reconfigurationmessage. Alternatively, the EUTRA cell 1 m-02 may add information abouta PLMN suitable to the UE 1 m-01 to the system information and transmitthe system information by including the system information in the RRCconnection reconfiguration message. For example, when only theinformation about a PLMN is included and the NR frequency band (list) orNR frequency range for (NG)EN-DC is not included, the UE 1 m-01 maydetermine that the NR frequency band (list) or NR frequency range for(NG)EN-DC supporting each PLMN is the same as information included insystem information received before transiting to the RRC connected mode.Obviously, the EUTRA cell 1 m-02 may add information about a PLMN and anNR frequency band (list) or NR frequency range for (NG)EN-DC for a newPLMN to system information, and transmit the system information to theUE 1 m-01 by adding the system information in the RRC connectionreconfiguration message.

In operation 1 m-25, the RRC connection reconfiguration message may notinclude mobilityControlInfo but may include the system informationincluding the NR frequency band (list) or NR frequency range supporting(NG)EN-DC.

FIG. 1N is a block diagram showing an internal structure of a UE,according to an embodiment of the disclosure.

Referring to FIG. 1N, the UE includes a radio frequency (RF) processor 1n-10, a baseband processor 1 n-20, a storage 1 n-30, and a controller 1n-40. In an embodiment, the controller 1 n-40 may include amulti-connection processor 1 n-42.

The RF processor 1 n-10 may perform functions for transmitting andreceiving signals through radio channels, e.g., signal band conversionand amplification. That is, the RF processor 1 n-10 up-converts abaseband signal provided from the baseband processor 1 n-20, to an RFband signal and transmit the RF band signal through an antenna, anddown-converts an RF band signal received through an antenna, to abaseband signal. For example, the RF processor 1 n-10 may include atransmit filter, a receive filter, an amplifier, a mixer, an oscillator,a digital-to-analog converter (DAC), and an analog-to-digital converter(ADC). Although only a single antenna is illustrated in FIG. 1N, the UEmay include multiple antennas. The RF processor 1 n-10 may include aplurality of RF chains. The RF processor 1 n-10 may perform beamforming.For beamforming, the RF processor 1 n-10 may adjust phases andamplitudes of signals transmitted or received through multiple antennasor antenna elements. The RF processor 1 n-10 may perform a MIMOoperation and may receive several layers while performing the MIMOoperation.

The baseband processor 1 n-20 may convert between a baseband signal anda bitstream based on physical layer specifications of a system. Forexample, for data transmission, the baseband processor 1 n-20 generatescomplex symbols by encoding and modulating a transmit bitstream. Fordata reception, the baseband processor 1 n-20 reconstructs a receivedbitstream by demodulating and decoding a baseband signal provided fromthe RF processor 1 n-10. For example, according to an OFDM scheme, fordata transmission, the baseband processor 1 n-20 generates complexsymbols by encoding and modulating a transmit bitstream, maps thecomplex symbols to subcarriers, and then configures OFDM symbols byperforming inverse fast Fourier transformation (IFFT) and cyclic prefix(CP) insertion. For data reception, the baseband processor 1 n-20 maysplit a baseband signal provided from the RF processor 1 n-10, in OFDMsymbol units, reconstruct signals mapped to subcarriers by performingfast Fourier transformation (FFT), and then reconstruct a receivedbitstream by demodulating and decoding the signals.

The baseband processor 1 n-20 and the RF processor 1 n-10 transmit andreceive signals as described above. As such, each of the basebandprocessor 1 n-20 and the RF processor 1 n-10 may also be called atransmitter, a receiver, a transceiver, or a communicator. At least oneof the baseband processor 1 n-20 or the RF processor 1 n-10 may includemultiple communication modules to support multiple different radioaccess technologies. Also, at least one of the baseband processor 1 n-20or the RF processor 1 n-10 may include multiple communication modules toprocess signals of different frequency bands. For example, the differentradio access technologies may include wireless LAN (For example, IEEE802.11), a cellular network (for example, LTE), and the like. Thedifferent frequency bands may include a super high frequency (SHF)(e.g., 2.5 GHz and 5 GHz) band and an mmWave (e.g., 60 GHz) band.

The storage 1 n-30 may store data for operation of the UE, e.g., basicprograms, application programs, and configuration information. Inparticular, the storage 1 n-30 may store information related to a secondaccess node performing wireless communication by using a second wirelessaccess technology. The storage 1 n-30 may provide the stored data uponrequest by the controller 1 n-40.

The controller 1 n-40 may control overall operations of the UE. Forexample, the controller 1 n-40 may transmit and receive signals throughthe baseband processor 1 n-20 and the RF processor 1 n-10. Thecontroller 1 n-40 may record and read data on and from the storage 1n-30. In this regard, the controller 1 n-40 may include at least oneprocessor. For example, the controller 1 n-40 may include acommunication processor (CP) for controlling communications and anapplication processor (AP) for controlling an upper layer such as anapplication program.

FIG. 1O is a block diagram of a configuration of an LTE or NR basestation, according to an embodiment of the disclosure.

As shown in FIG. 1O, the base station may include an RF processor 1o-10, a baseband processor 1 o-20, a backhaul communicator 1 o-30, astorage 1 o-40, and a controller 1 o-50. In an embodiment, thecontroller 1 o-50 may include a multi-connection processor 1 o-52.

The RF processor 1 o-10 may perform functions for transmitting andreceiving signals through radio channels, e.g., signal band conversionand amplification. That is, the RF processor 1 o-10 up-converts abaseband signal provided from the baseband processor 1 o-20, to an RFband signal and transmit the RF band signal through an antenna, anddown-converts an RF band signal received through an antenna, to abaseband signal. For example, the RF processor 1 o-10 may include atransmit filter, a receive filter, an amplifier, a mixer, an oscillator,a DAC, and an ADC. Although only a single antenna is illustrated in FIG.1O, the base station may include multiple antennas. The RF processor 1o-10 may include a plurality of RF chains. In addition, the RF processor1 o-10 may perform beamforming. For beamforming, the RF processor 1 o-10may adjust phases and amplitudes of signals transmitted or receivedthrough multiple antennas or antenna elements. The RF processor 1 o-10may perform a downlink MIMO operation by transmitting at least onelayer.

The baseband processor 1 o-20 may convert between a baseband signal anda bitstream based on physical layer specifications of a first radioaccess technology. For example, for data transmission, the basebandprocessor 1 o-20 generates complex symbols by encoding and modulating atransmit bitstream. For data reception, the baseband processor 1 o-20reconstructs a received bitstream by demodulating and decoding abaseband signal provided from the RF processor 1 o-10. For example,according to an OFDM scheme, for data transmission, the basebandprocessor 1 o-20 generates complex symbols by encoding and modulating atransmit bitstream, maps the complex symbols to subcarriers, and thenconfigures OFDM symbols by performing IFFT and CP insertion. For datareception, the baseband processor 1 o-20 may split a baseband signalprovided from the RF processor 1 o-10, in OFDM symbol units, reconstructsignals mapped to subcarriers by performing FFT, and then reconstruct areceived bitstream by demodulating and decoding the signals. Thebaseband processor 1 o-20 and the RF processor 1 o-10 transmit andreceive signals as described above. As such, each of the basebandprocessor 1 o-20 and the RF processor 1 o-10 may also be called atransmitter, a receiver, a transceiver, a communicator, or a wirelesscommunicator.

The backhaul communicator 1 o-30 may provide an interface forcommunicating with other nodes in a network. In other words, thebackhaul communicator 1 o-30 may convert a bit string transmitted from amain base station to another node, for example, an auxiliary basestation or a core network, into a physical signal, and convert aphysical signal received from the other node into a bit string.

The storage 1 o-40 may store data for operation of the main basestation, e.g., basic programs, application programs, and configurationinformation. In particular, the storage 1 o-40 may store informationabout bearers allocated for a connected UE, a measurement reporttransmitted from the connected UE, etc. The storage 1 o-40 may storecriteria information used to determine whether to provide or releasemulti-connection to or from the UE. The storage 1 o-40 may provide thestored data upon request by the controller 1 o-50.

The controller 1 o-50 may control overall operations of the main basestation. For example, the controller 1 o-50 may transmit and receivesignals through the baseband processor 1 o-20 and the RF processor 1o-10 or through the backhaul communicator 1 o-30. The controller 1 o-50may record and read data on and from the storage 1 o-40. In this regard,the controller 1 o-50 may include at least one processor.

Although the present disclosure has been described with variousembodiments, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

1. A terminal for cell reselection in a wireless communication system,the terminal comprising: a transceiver; and at least one processorconfigured to: select a public land mobile network (PLMN) in an idlemode or an inactive mode, receive, from a base station, a PLMN identitylist including one or more pieces of PLMN identity information via afirst type system information block, wherein each of the one or morepieces of PLMN identity information includes a PLMN identity for acorresponding PLMN, and the one or more pieces of PLMN identityinformation are listed in a first order for PLMN(s), receive, from thebase station, a PLMN information list including one or more pieces ofPLMN information via a third type system information block, wherein eachof the one or more pieces of PLMN information includes a New Radio (NR)frequency band list for a corresponding PLMN and the one or more piecesof PLMN information is listed in a same order as the first order forPLMN(s) in which the one or more pieces of PLMN identity information arelisted in the PLMN identity list received via the first type systeminformation block, determine whether a first NR frequency band list forthe selected PLMN is included in the PLMN information list and whetherthe terminal supports to operate in Evolved Universal Terrestrial RadioAccess (E-UTRA)-NR dual connectivity (EN-DC) by using a serving cell andat least one NR frequency band in the first NR frequency band list, whenthe first NR frequency band list for the selected PLMN is included inthe PLMN information list and the terminal supports to operate in theEN-DC by using the serving cell and the at least one NR frequency bandfor the selected PLMN, transmit, to a upper layer, a upper layerindication, and when the first NR frequency band list for the selectedPLMN is not included in the PLMN information list or the terminal doesnot support to operate in the EN-DC by using the serving cell and the atleast one NR frequency band for the selected PLMN, transmit, to theupper layer, information indicating absence of the upper layerindication.
 2. The terminal of claim 1, wherein the at least oneprocessor is further configured to: receive, from the base station, theupper layer indication via a second type system information block, andwhen the first NR frequency band list for the selected PLMN is includedin the PLMN information list and the terminal supports to operate in theEN-DC by using the serving cell and the at least one NR frequency bandfor the selected PLMN, transmit, to the upper layer, the upper layerindication regardless of the received upper layer indication, whereinthe received upper layer indication is an indication to the upper layerthat a cell for the selected PLMN offers NR capabilities.
 3. Theterminal of claim 1, wherein the at least one processor is furtherconfigured to: receive, from the base station, a radio resource control(RRC) connection reconfiguration message including informationassociated with NR configuration, determine whether the terminal isconfigured to operate in the EN-DC based on the RRC connectionreconfiguration message, transmit, to the upper layer, the upper layerindication when the terminal is configured to operate in the EN-DC, andtransmit, to the upper layer, information indicating absence of theupper layer indicator when the terminal is not configured to operate inthe EN-DC.
 4. The terminal of claim 3, wherein the informationassociated with NR configuration is transmitted to the terminal in aconnected mode within the RRC connection reconfiguration message when atleast one NR frequency band for the selected PLMN is supported.
 5. Theterminal of claim 3, wherein the at least one processor is furtherconfigured to transmit, to the base station, capability informationcomprising at least one of information indicating whether the terminalsupports the EN-DC or information including NR bands supported by theterminal in the EN-DC.
 6. A base station for cell reselection in awireless communication system, comprising: a transceiver; and at leastone processor configured to: transmit, to a terminal, a public landmobile network (PLMN) identity list including one or more pieces of PLMNidentity information via a first type system information block, whereineach of the one or more pieces of PLMN identity information includes aPLMN identity for a corresponding PLMN, and the one or more pieces ofPLMN identity information are listed in a first order for PLMN(s), andtransmit, to the terminal, a PLMN information list including one or morepieces of PLMN information via a third type system information block,wherein each of the one or more pieces of PLMN information includes aNew Radio (NR) frequency band list for a corresponding PLMN and the oneor more pieces of PLMN information are listed in a same order as thefirst order for PLMN(s) in which the one or more pieces of PLMN identityinformation are listed in the PLMN identity list received via the firsttype system information block, wherein, when a first NR frequency bandlist for a PLMN selected by the terminal is included in the PLMNinformation list and the terminal supports to operate in EvolvedUniversal Terrestrial Radio Access (E-UTRA)-NR dual connectivity (EN-DC)by using a serving cell and at least one NR frequency band in the NRfrequency band list, a upper layer indication is transmitted to a upperlayer of the terminal, and wherein, when the first NR frequency bandlist for the PLMN selected by the terminal is not included in the PLMNinformation list or the terminal does not support to operate in theEN-DC by using the serving cell and the at least one NR frequency bandin the first NR frequency band list, information indicating absence ofthe upper layer indication is transmitted to the upper layer of theterminal.
 7. The base station of claim 6, wherein the at least oneprocessor is further configured to transmit, to the terminal, the upperlayer indication via a second type system information block, andwherein, when the first NR frequency band list for the PLMN selected bythe terminal is included in the PLMN information list and the terminalsupports to operate in the EN-DC by using the serving cell and the atleast one NR frequency in the first NR frequency band list, the upperlayer indication is received by the upper layer of the terminalregardless of the transmitted upper layer indication, and wherein theupper layer indication is an indication to the upper layer that a cellfor the PLMN selected by the terminal offers NR capabilities.
 8. Thebase station of claim 6, wherein the at least one processor is furtherconfigured to transmit, to the terminal, a radio resource control (RRC)connection reconfiguration message including information associated withNR configuration, wherein, when the terminal is configured to operate inthe EN-DC based on the information associated with NR configuration, theupper layer indication is transmitted to the upper layer of theterminal, and wherein, when the terminal is not configured to operate inthe EN-DC based on the information associated with NR configuration, theinformation indicating absence of the upper layer indicator istransmitted to the upper layer of the terminal.
 9. The base station ofclaim 8, wherein the information associated with NR configuration istransmitted to the terminal in a connected mode within the RRCconnection reconfiguration message when at least one NR frequency bandfor the selected PLMN is supported.
 10. The base station of claim 8,wherein the at least one processor is further configured to receive,from the terminal, capability information comprising at least one ofinformation indicating whether the terminal supports the EN-DC orinformation including NR bands supported by the terminal in the EN-DC.11. A method, performed by a terminal, for cell reselection in awireless communication system, the method comprising: selecting a publicland mobile network (PLMN) in an idle mode or an inactive mode;receiving, from a base station, a PLMN identity list including one ormore pieces of PLMN identity information via a first type systeminformation block, wherein each of the one or more pieces of PLMNidentity information includes a PLMN identity for a corresponding PLMN,and the one or more pieces of PLMN identity information are listed in afirst order for PLMN(s); receiving, from the base station, a PLMNinformation list including one or more pieces of PLMN information via athird type system information block, wherein each of the one or morepieces of PLMN information includes a New Radio (NR) frequency band listfor a corresponding PLMN and the one or more pieces of PLMN informationis listed in a same order as the first order for PLMN(s) in which theone or more pieces of PLMN identity information are listed in the PLMNidentity list received via the first type system information block;determining whether a first NR frequency band list for the selected PLMNis included in the PLMN information list and whether the terminalsupports to operate in Evolved Universal Terrestrial Radio Access(E-UTRA)-NR dual connectivity (EN-DC) by using a serving cell and atleast one NR frequency band in the first NR frequency band list; whenthe first NR frequency band list for the selected PLMN is included inthe PLMN information list and the terminal supports to operate in theEN-DC by using a serving cell and the at least one NR frequency band inthe first NR frequency band list, transmitting, to a upper layer, aupper layer indication; and when the first NR frequency band list forthe selected PLMN is not included in the PLMN information list or theterminal does not support to operate in the EN-DC by using the servingcell and the at least one NR frequency band for the selected PLMN,transmitting, to the upper layer, information indicating absence of theupper layer indication.
 12. The method of claim 11, further comprisingreceiving, from the base station, the upper layer indication via asecond type system information block, wherein the transmitting the upperlayer indication comprises, when the first NR frequency band list forthe selected PLMN is included in the PLMN information list and theterminal supports to operate in the EN-DC by using the serving cell andthe at least one NR frequency band for the selected PLMN, transmitting,to the upper layer, the upper layer indication regardless of thereceived the upper layer indication, and wherein the upper layerindication is an indication to the upper layer that a cell for theselected PLMN offers NR capabilities.
 13. The method of claim 11,further comprising: receiving, from the base station, a radio resourcecontrol (RRC) connection reconfiguration message including informationassociated with NR configuration; determining whether the terminal isconfigured to operate in the EN-DC based on the RRC connectionreconfiguration message; transmitting, to the upper layer, the upperlayer indication when the terminal is configured to operate in theEN-DC; and transmitting, to the upper layer, information indicatingabsence of the upper layer indicator when the terminal is not configuredto operate in the EN-DC.
 14. The method of claim 13, wherein theinformation associated with NR configuration is transmitted to theterminal in a connected mode within the RRC connection reconfigurationmessage when at least one NR frequency band for the selected PLMN issupported.
 15. The method of claim 13, further comprising transmitting,to the base station, capability information comprising at least one ofinformation indicating whether the terminal supports the EN-DC orinformation including NR bands supported by the terminal in the EN-DC.16. A method, performed by a base station, for cell reselection in awireless communication system, the method comprising: transmitting, to aterminal, a public land mobile network (PLMN) identity list includingone or more pieces of PLMN identity information via a first type systeminformation block, wherein each of the one or more pieces of PLMNidentity information includes a PLMN identity for a corresponding PLMN,and the one or more pieces of PLMN identity information are listed in afirst order for PLMN(s); and transmitting, to the terminal, a PLMNinformation list including one or more pieces of PLMN information via athird type system information block, wherein each of the one or morepieces of PLMN information includes a New Radio (NR) frequency band listfor a corresponding PLMN and the one or more pieces of PLMN informationare listed in a same order as the first order for PLMN(s) in which theone or more pieces of PLMN identity information are listed in the PLMNidentity list received via the first type system information block,wherein, when a first NR frequency band list for a PLMN selected by theterminal is included in the PLMN information list and the terminalsupports to operate in Evolved Universal Terrestrial Radio Access(E-UTRA)-NR dual connectivity (EN-DC) by using a serving cell and atleast one NR frequency band in the first NR frequency band list, a upperlayer indication is transmitted to a upper layer of the terminal, andwherein, when the first NR frequency band list for the PLMN selected bythe terminal is not included in the PLMN information list or theterminal does not support to operate in the EN-DC by using the servingcell and the at least one NR frequency band in the first NR frequencyband list, information indicating absence of the upper layer indicationis transmitted to the upper layer of the terminal.
 17. The method ofclaim 16, further comprising transmitting, to the terminal, the upperlayer indication via a second type system information block, wherein,when the first NR frequency band list for the PLMN selected by theterminal is included in the PLMN information list and the terminalsupports to operate in the EN-DC by using the serving cell and the atleast one NR frequency in the first NR frequency band list, the upperlayer indication is received by the upper layer of the terminalregardless of the transmitted upper layer indication, and wherein theupper layer indication is an indication to the upper layer that a cellfor the PLMN selected by the terminal offers NR capabilities.
 18. Themethod of claim 16, further comprising transmitting, to the terminal, aradio resource control (RRC) connection reconfiguration messageincluding information associated with NR configuration, wherein, whenthe terminal is configured to operate in the EN-DC based on theinformation associated with NR configuration, the upper layer indicationis transmitted to the upper layer of the terminal, and wherein, when theterminal is not configured to operate in the EN-DC based on theinformation associated with NR configuration, the information indicatingabsence of the upper layer indicator is transmitted to the upper layerof the terminal.
 19. The method of claim 18, wherein the informationassociated with NR configuration is transmitted to the terminal in aconnected mode within the RRC connection reconfiguration message when atleast one NR frequency band for the selected PLMN is supported.
 20. Themethod of claim 18, further comprising receiving, from the terminal,capability information comprising at least one of information indicatingwhether the terminal supports the EN-DC or information including NRbands supported by the terminal in the EN-DC.